Little predatory bird, swallow biting leg off (6)
I believe the answer is:
eaglet
'little predatory bird' is the definition.
(a young eagle)
'swallow biting leg off' is the wordplay.
'swallow' becomes 'eat' (I've seen this in another clue).
'biting' means one lot of letters goes inside another (I've seen this in other clues).
'off' indicates anagramming the letters.
'leg' anagrammed gives 'gle'.
'eat' placed around 'gle' is 'EAGLET'.
(Other definitions for eaglet that I've seen before include "Get ale for the young bird" , "Fledgling" , "young flier?" , "Bird still in nest" , "Eyrie resident" .)