Excellent department led by ace (5)
I believe the answer is:
adept
'excellent' is the definition.
(thesaurus)
'department led by ace' is the wordplay.
'department' becomes 'dept' (**).
'led by' is a charade indicator (letters next to each other).
'ace' becomes 'a'.
'dept' put after 'a' is 'ADEPT'.
(Other definitions for adept that I've seen before include "Practised" , "Proficient, skilled" , "One highly skilled could be taped" , "skilled performer" , "Very skilful, proficient" .)