Soft buttocks alongside? Ignore (4,2)
I believe the answer is:
pass by
'ignore' is the definition.
(I've seen this in another clue)
'soft buttocks alongside?' is the wordplay.
'soft' becomes 'p' (musical abbreviation for 'piano').
'buttocks' becomes 'ass' (synonyms).
'alongside?' becomes 'by' (I've seen this in other clues).
'p'+'ass'+'by'='PASS BY'
(Other definitions for pass by that I've seen before include "neglect" , "Don't stop to talk to someone" , "''Cast a cold eye / On life, on death / Horseman ... ... (WB Yeats)" , "Go on and leave alone" , "Go past - disregard" .)