Day before a diet, nuts gorged (8)
I believe the answer is:
satiated
'gorged' is the definition.
('satiate' can be a synonym of 'gorge')
'day before a diet nuts' is the wordplay.
'day' becomes 'sat' (I've seen this before**).
'before' is a charade indicator (letters next to each other).
'nuts' is an anagram indicator (nuts can mean crazy).
'a'+'diet'='adiet'
'adiet' anagrammed gives 'iated'.
'sat'+'iated'='SATIATED'
(Other definitions for satiated that I've seen before include "Filled to repletion" , "Too full, having eaten excessively" , "Stuffed, glutted" , "Glutted or cloyed with excess (8)" , "Replete or surfeited" .)