Bird ingesting large bean or nut (5)
I believe the answer is:
clock
'bean or nut' is the definition.
(both can refer to a type of seed)
'bird ingesting large' is the wordplay.
'bird' becomes 'cock' (cock is a kind of bird**).
'ingesting' means one lot of letters goes inside another.
'large' becomes 'l'.
'cock' going around 'l' is 'CLOCK'.
(Other definitions for clock that I've seen before include "one displaying speed" , "Flashy black-market dealer" , "Striker" , "Time-teller" , "Notice" .)