Bring on bird with no head and backside (6)
I believe the answer is:
entail
'bring' is the definition.
(thesaurus)
'bird with no head and backside' is the wordplay.
'bird' becomes 'hen' (hen is a kind of bird).
'with no head' means to remove the first letter.
'and' is a charade indicator (letters next to each other).
'backside' becomes 'tail' (synonyms).
'hen' with its first letter taken off is 'en'.
'en'+'tail'='ENTAIL'
'on' acts as a link.
(Other definitions for entail that I've seen before include "Estate settled" , "outmoded fashion" , "Call for" , "Bring on an inevitable consequence" , "Late in (anag.)" .)