Complete club ousting leader (5)
I believe the answer is:
utter
'complete' is the definition.
(I've seen this in other clues)
'club ousting leader' is the wordplay.
'club' becomes 'putter' (a golf club).
'ousting leader' means to remove the first letter.
'putter' with its initial letter taken away is 'UTTER'.
(Other definitions for utter that I've seen before include "Complete; absolute" , "Say; total" , "Declare - total" , "Absolute - say" , "Sheer" .)