Exploits when holding court (4)
I believe the answer is:
acts
'exploits' is the definition.
(I've seen this before)
'when holding court' is the wordplay.
'when' becomes 'as'.
'holding' indicates putting letters inside.
'court' becomes 'ct'.
'as' placed around 'ct' is 'ACTS'.
(Other definitions for acts that I've seen before include "exerts influence" , "bands, comedians, etc" , "[BOOK] of the 26 [BIBLE]" , "Deeds; book of the Bible" , "Cast in major play sections" .)