Yield readily at first, arrested by police officer (4)
I believe the answer is:
crop
'yield' is the definition.
(crop is a kind of yield)
'readily at first arrested by police officer' is the wordplay.
'at first' suggests taking the first letters.
'arrested by' indicates putting letters inside (I've seen this in other clues).
'police officer' becomes 'cop' (cop is a kind of police officer**).
The initial letter of 'readily' is 'r'.
'r' placed within 'cop' is 'CROP'.
(Other definitions for crop that I've seen before include "Yield from a single growing season" , "Season's produce" , "Set" , "Bird's gullet pouch" , "Yield from cultivation" .)