Dislodge from behind piano (4)
I believe the answer is:
bump
'dislodge' is the definition.
(synonyms)
'behind piano' is the wordplay.
'behind' becomes 'bum' (synonyms).
'piano' becomes 'p' (musical abbreviation).
'bum'+'p'='BUMP'
'from' is the link.
(Other definitions for bump that I've seen before include "Slight collision" , "Raised mark left by blow" , "Evidence of pregnancy - knock (into)" , "Thud down, into" , "Collide - protuberance" .)