Manage to protect small thicket (5)
I believe the answer is:
copse
'thicket' is the definition.
('copse' can be a synonym of 'thicket')
'manage to protect small' is the wordplay.
'manage' becomes 'cope' ('cope' can be a synonym of 'manage'**).
'to protect' is an insertion indicator.
'small' becomes 's' (abbreviation - e.g. clothes size).
'cope' going around 's' is 'COPSE'.
(Other definitions for copse that I've seen before include "Piece of managed woodland" , "Small thicket" , "Small group of trees" , "Wood - thicket" , "spinney" .)