Manage to capture Serbian leader in thicket (5)
I believe the answer is:
copse
'thicket' is the definition.
('copse' can be a synonym of 'thicket')
'manage to capture serbian leader' is the wordplay.
'manage' becomes 'cope' ('cope' can be a synonym of 'manage'**).
'to capture' is an insertion indicator.
'leader' indicates taking the first letters.
The initial letter of 'serbian' is 's'.
'cope' placed around 's' is 'COPSE'.
'in' is the link.
(Other definitions for copse that I've seen before include "Scope for a small wood" , "Cluster of trees" , "Wood - thicket" , "Cultivated woodland area" , "Piece of woodland used for cutting" .)