About 150 gatecrash function for kicks (7)
I believe the answer is:
recoils
'kicks' is the definition.
(kick can mean a gun recoiling)
'about 150 gatecrash function' is the wordplay.
'about' becomes 're' ('re' means regarding or about).
'r50' becomes 'IL' (Roman numerals for r and 50).
'gatecrash' means one lot of letters goes inside another (inserted letters gatecrash their way in).
'function' becomes 'cos' (mathematical function).
'il' placed within 'cos' is 'coils'.
're'+'coils'='RECOILS'
'for' is the link.
(Other definitions for recoils that I've seen before include "Jerks backwards" , "Moves or springs suddenly back, perhaps in fear" , "Flinches" , "Staggers back" , "Draws back in disgust" .)