Group must accept it's wrong - send rude message ... (4)
I believe the answer is:
Here is my best explanation:
'message' is the definition.
(I have seen 'Explicit message' mean 'sext' so perhaps 'message' could also mean 'sext')
'group must accept it's wrong' is the wordplay.
'group' becomes 'set'.
'must accept' is an insertion indicator.
'it's wrong' becomes 'x'.
'set' enclosing 'x' is 'SEXT'.
'send rude' acts as a link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?