Naval threats, according to an old saying / WED 3-27-24 / Release following the GameCube / T that comes before Y / Characteristic sound of Yoko Ono? / Chum, in Champagne

• SKIN tight (9A: *Closefitting)
• "HANG tight!" (35A: *"Don't go anywhere!")
• "SLEEP tight" (64A: *Rhyming partner of "Good night")
• Loose TOOTH (13A: *Wiggler in a child's mouth)
• Loose LEAF (39A: *Like some paper and tea)
• Loose LIPS (65A: *Naval threats, according to an old saying) 

Loose lips sink ships is an American English idiom meaning "beware of unguarded talk". The phrase originated on propaganda posters during World War II, with the earliest version using the wording loose lips might sink ships. The phrase was created by the War Advertising Council and used on posters by the United States Office of War Information.

This type of poster was part of a general campaign to advise servicemen and other citizens to avoid careless talk that might undermine the war effort. There were many similar such slogans, but "Loose lips sink ships" remained in the American idiom for the remainder of the century and into the next, usually as an admonition to avoid careless talk in general.(The British equivalent used "Careless Talk Costs Lives", and variations on the phrase "Keep mum", while in neutral Sweden the State Information Board promoted the wordplay "En svensk tiger" ("A Swedish tiger" or "A Swede keeps silent": the Swedish word "tiger" means both "tiger" and "keeps silent"), and Germany used "Schäm Dich, Schwätzer!" (English: "Shame on you, blabbermouth!").

However, propaganda experts at the time and historians since have argued the main goal of these and similar posters was to actually frighten people into not spreading rumors, even true ones, containing bad news that might hurt morale or create tension between groups of Americans, since the Federal Bureau of Investigation (in charge of dealing with enemy spies) had rounded up the key agents in June 1941, so that the nation "entered the war with confidence that there was no major German espionage network hidden in U.S. society." [...] 

Historian D'Ann Campbell argues that the purpose of the wartime posters, propaganda, and censorship of soldiers' letters was not to foil spies but "to clamp as tight a lid as possible on rumors that might lead to discouragement, frustration, strikes, or anything that would cut back military production." (wikipedia)

[note: doubling OTOH with IMHO later on did not, I repeat not, make things better]

Only-for-the-vowels IONIAN, the dreaded ON TOE ... this is the kind of tiresome short stuff that longtime solvers will have become inured to over the years, but I think a lot about people who aren't longtime solvers and how crummy this fill must seem. Plus, there's no reason to accept bad fill as a standard in the most high-profile crossword in the country. Again, it's a matter of density here—no one answer in particular, but a concatenation, a barrage. True, the NW is the worst of it, but the olden/boring fill is everywhere, as if the puzzle is barely holding itself together to accommodate the theme ... only the theme isn't really that demanding. Yes, you have not just three longer answers, but the six short ones that are more or less fixed in place. That does put stress on the grid. But it's your job to make the effects of that stress near invisible, particularly in a grid that doesn't actually hold any good fill at all beyond the instructions / revealer. It is fun (in a way) to discover the right/left gimmick, so you don't necessarily need sparkly fill today. But you do need it all to groan a little less.