A general hint:  Always take a quick look down the whole list of clues to see if there’s one that indicates a “theme” for the puzzle.  On Thursdays one always has to be on the lookout for something that’s a help in “getting” whatever trick the puzzle-maker is up to.  Of course, as the cruelty of life would have it, there is no “special clue” that guides us to the theme.   (By the way:  You can rarely get the answer to the special “key” clue from the clue itself.  That will come much later in solving the puzzle.)

First, an admission, I’m 3/4 of the way through the puzzle and still don’t have a clue about it’s theme.  Though I can see something’s wrong…seemingly impossible combinations of answers, but then these have gradually resolved…still no obvious rebus (one square containing a symbol, or, more commonly, several letters)

Well, now that I’m done (full disclosure:  I hit the “check button” several times and found several entries wrong),  I only now understand the theme, after staring at the completed puzzle for a while.  There are several answers that don’t really work without the little wordplay going on between an across answer and a down answer.  Now that I see it, it’s pretty clever. 

This isn’t a hint exactly, but there are a lot of specific clues and answers I’d personally never heard, or, in one case couldn’t remember and probably won’t remember tomorrow either!

Meanwhile, a few individual hints:

lament after a loss, maybe:  2 words; remember that lament can be more than one part of speech

Like un + quatre vis-å-vis deux + trois:  You knew you’d need those damn French (and Italian, and Spanish, and a few German ones also) sooner or later.  But what’s worse, even if you figure out what the numbers are you still don’t know the French word for what they are.  Well, the French words sounds a lot like the English world of the same meaning.

Something generally known:  2 words

Hearing problems?:  (I case you don’t know, question marks indicate that the clue / answer combo is a little bit of a pun, a weak joke.)  For these kinds of hearing problem, you don’t need an ENT.

Like a buzz, say:  Don’t think either saw or bee.

Agenda’s beginning or end: Well’ it’s not a long “a,”  but it’s also just one word, a word plus a letter.