Restriction some broccoli mitigates (5)
I believe the answer is:
limit
'restriction' is the definition.
(I've seen this before)
'some broccoli mitigates' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'LIMIT' is hidden within 'broccoli mitigates'.
(Other definitions for limit that I've seen before include "verge" , "speed restriction applied" , "Extreme point" , "Breaking point" , "Place bound on" .)