Judges and half-cut bosses on donkeys (8)
I believe the answer is:
assesses
'judges' is the definition.
(assessing is a kind of judging)
'half-cut bosses on donkeys' is the wordplay.
'half cut' means to take half the letters.
'on' says to put letters next to each other.
'donkeys' becomes 'asses' (I've seen this before).
'bosses' cut in half is 'ses'.
'ses' put after 'asses' is 'ASSESSES'.
'and' acts as a link.
(Other definitions for assesses that I've seen before include "Judges the worth of" , "Carries out tests" .)