Guy ousting leader is clever (4)
I believe the answer is:
able
'clever' is the definition.
(able can mean skilled or talented)
'guy ousting leader' is the wordplay.
'guy' becomes 'cable' (I've seen this in other clues).
'ousting leader' means to remove the first letter (to oust is to remove).
'cable' with its initial letter removed is 'ABLE'.
'is' acts as a link.
(Other definitions for able that I've seen before include "Fitted" , "Efficient" , "Proficient; skilful" , "Of high proficiency" , "See 21" .)