A part of song opposed (6)
I believe the answer is:
averse
'opposed' is the definition.
(synonyms)
'a part of song' is the wordplay.
'part of song' becomes 'verse' (I've seen this before).
'a'+'verse'='AVERSE'
(Other definitions for averse that I've seen before include "Indisposed" , "Not keen" , "Unwilling or disinclined, perhaps to hard work" , "Not in favour of" , "'Opposed, disinclined (6)'" .)