Fools judge, briefly (5)
I believe the answer is:
asses
'fools' is the definition.
(ass is a kind of fool)
'judge briefly' is the wordplay.
'judge' becomes 'assess' (assessing is a kind of judging).
'briefly' means to remove the last letter.
'assess' with its final letter taken off is 'ASSES'.
(Other definitions for asses that I've seen before include "not the most sensible types" , "Pompous fools" , "More than one fool" , "Small, sure-footed animals" , "Animals of horse family" .)