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 present in the answer.
The remaining letters 'sext' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
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" .)