Three couples send rude messages on film (6)
I believe the answer is:
sextet
'three couples' is the definition.
(I've seen this before)
'send rude messages on film' is the wordplay.
I cannot quite see how this works, but
'film' could be 'et' (E.T. the Extra-Terrestrial) and 'et' is found within the answer.
The remaining letters 'sext' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for sextet that I've seen before include "Group of six (X, not S)" , "Music for six" , "Piece for six" , "Musical group" , "Musical work" .)