Songbird left in trap (6)
I believe the answer is:
linnet
'songbird' is the definition.
(I've seen this before)
'left in trap' is the wordplay.
'left' becomes 'l' (common abbreviation).
'trap' becomes 'net' (net is a kind of trap).
'l'+'in'+'net'='LINNET'
(Other definitions for linnet that I've seen before include "A British finch" , "Passerine bird" , "Winger" , "See three down" , "Brown-grey kind of finch" .)