Criminal swindle -- then never-ending bird (6)
I believe the answer is:
condor
'bird' is the definition.
(condor is a kind of bird)
'criminal swindle then never-ending' is the wordplay.
'criminal' becomes 'con' (abbreviation for 'convict'**).
'swindle' becomes 'do'.
'then' means one lot of letters go next to another.
'ending' suggests the final letters.
The final letter of 'never' is 'r'.
'con'+'do'+'r'='CONDOR'
(Other definitions for condor that I've seen before include "Large bird of prey" , "Large flyer" , "Andean bird" , "South American vulture" , "Andean vulture" .)