Leaves one prisoner about to be surrounded by enemy (7)
I believe the answer is:
foliage
'leaves' is the definition.
(I've seen this before)
'one prisoner about to be surrounded by enemy' is the wordplay.
'one' becomes 'i' (Roman numeral).
'prisoner' becomes 'lag' (I've seen this before).
'about' indicates putting letters inside.
'to be surrounded by' indicates putting letters inside.
'enemy' becomes 'foe' (I've seen this before).
'i' going into 'lag' is 'liag'.
'liag' placed within 'foe' is 'FOLIAGE'.
(Other definitions for foliage that I've seen before include "Plant leaves collectively" , "Cluster of leaves" , "(Decorative) leaves" , "Leaves of tree or plant" , "Greenery, leaves of trees or plants" .)