Can you tell spymaster you know the word they gave a clue for?
Field Operatives are only allowed to discuss the clue after their Spymaster provides it, until their team's turn is over.

Rules, P.4
"MAKING CONTACT

When the spymaster gives a clue, his or her field operatives try to figure out what it means. They can debate it amongst themselves..."

Same page:
"Number of Guesses

...Any wrong guess ends the turn immediately..."

This is reiterated and summarized on page 5:
"GAME FLOW

Spymasters take turns giving clues. After
a spymaster gives a clue, his or her team starts
guessing. Their turn ends when they guess
wrong, when they decide to stop, or when they
have made the maximum number of guesses
for that clue. Then it is the other team's turn"

Any other discussion of a previous clue, during another team's turn or on an operative's own turn prior to the new clue being read, is therefore out of scope of the rules (i.e., it's not allowed).  This conveniently addresses any clue-related discussion among the operatives, but also any directed towards the spymaster (whether or not it is acknowledged by the spymaster).  This would apply equally to basically harmless and vague discussion like "Oh, I know what you meant now" or, taken to its logical conclusion, a field operative explicitly instructing their spymaster to add 1 to the number of guesses on their new clue (effectively providing +2 potential guesses).

So if you're a field operative, unless you want to talk about getting snacks for the table when it isn't your turn or before your team's clue is read, don't say anything!