Experts break the case (4)
I believe the answer is:
aces
'experts' is the definition.
(ace is a kind of expert)
'break the case' is the wordplay.
'break' is an anagram indicator.
'case' with letters rearranged gives 'ACES'.
(Other definitions for aces that I've seen before include "Champions" , "Flying war heroes" , "Ones or elevens in cards" , "Top (or bottom) cards" , "Experts (in their field)" .)