Remains from party bachelor left (3)
I believe the answer is:
ash
'remains' is the definition.
(I've seen this before)
'party bachelor left' is the wordplay.
'party' becomes 'bash' (bash is a kind of party).
'bachelor' becomes 'b' (abbreviation e.g. BA=Bachelor of Arts).
'left' is a deletion indicator.
'bash' with 'b' taken away is 'ASH'.
'from' acts as a link.
(Other definitions for ash that I've seen before include "Remains of conflagration" , "It's used for flooring" , "Woodland tree; result of burning" , "Fire's remains" , ". . . . [FOREST] One of which" .)