Leaves one enthralled by prisoner captured by enemy (7)
I believe the answer is:
foliage
'leaves' is the definition.
(I've seen this before)
'one enthralled by prisoner captured by enemy' is the wordplay.
'one' becomes 'i' (Roman numeral).
'enthralled by' means one lot of letters goes inside another ('enthral' can mean 'capture').
'prisoner' becomes 'lag' (I've seen this before).
'captured by' means one lot of letters goes inside another.
'enemy' becomes 'foe' (I've seen this before).
'i' going inside 'lag' is 'liag'.
'liag' going into 'foe' is 'FOLIAGE'.
(Other definitions for foliage that I've seen before include "Cluster of leaves" , "Plant leaves collectively" , "Green leaves" , "Leaves of tree or plant" , "Greenery, leaves of trees or plants" .)