Man off diet's rebuked (9)
I believe the answer is:
chastised
'rebuked' is the definition.
(chastising is a kind of rebuking)
'man off diet's' is the wordplay.
'man' becomes 'chas' ().
'off' indicates an anagram.
'diets' is an anagram of 'tised'.
'chas'+'tised'='CHASTISED'
(Other definitions for chastised that I've seen before include "Sad ethics (anag.)" , "Severely reprimanded" , "Rebuked" , "beaten" .)