Extra wicket is decisive, elevating leaders (4)
I believe the answer is:
wide
'extra' is the definition.
(cricket term)
'wicket is decisive elevating leaders' is the wordplay.
'leaders' suggests taking the first letters.
The first letters of 'wicket is decisive elevating' is 'WIDE'.
(Other definitions for wide that I've seen before include "(At cricket) an extra" , "Extensive" , "Far from the target" , "Spacious; an extra" , "Expansive" .)