African leader wins time in opposition (7)
I believe the answer is:
against
'in opposition' is the definition.
(I've seen this before)
'african leader wins time' is the wordplay.
'leader' suggests taking the first letters.
'wins' becomes 'gains' ('gain' can be a synonym of 'win').
'time' becomes 't'.
The initial letter of 'african' is 'a'.
'a'+'gains'+'t'='AGAINST'
(Other definitions for against that I've seen before include "Opposed" , "Disapproving of" , "close by" , "Con" , "Not favouring" .)