Ignore fool with bachelor among extremists in party (4,2)
I believe the answer is:
pass by
'ignore' is the definition.
(I've seen this in another clue)
'fool with bachelor among extremists in party' is the wordplay.
'fool' becomes 'ass' (both can mean a stupid person).
'with' is a charade indicator (letters next to each other).
'bachelor' becomes 'B' (abbreviation e.g. BA=Bachelor of Arts).
'among' is an insertion indicator (inserted letters are placed among others).
'extremists in' says to hollow out the word (remove centre letters).
'party' with its centre removed is 'py'.
'ass'+'b'='assb'
'assb' placed inside 'py' is 'PASS BY'.
(Other definitions for pass by that I've seen before include "Don't stop to talk to someone" , "Overlook; go beyond" , "Go past - disregard" , "Go on and leave alone" , "Ignore, overlook" .)