Clique member cool with scrumpy they say (7)
I believe the answer is:
Here is my best explanation:
'clique member' is the definition.
'cool with scrumpy they say' is the wordplay.
'cool' becomes 'in' (I've seen this in other clues).
'with' means one lot of letters go next to another.
'scrumpy' becomes 'cider' (I've seen this before).
'they say' indicates a 'sounds like' (homophone) clue.
'cider' sounds like 'sider'.
(Other definitions for insider that I've seen before include "member of favoured group?", "person with the lowdown", "Dire sin (anag)", "Accepted member of group, in the know", "One dealing illegally", "Doing time, right, for this", "Possible mole", "Member of select group in the know", "Member of charmed circle" and "One with special knowledge".)