Military volunteers man captured (5)
I believe the answer is:
taken
'captured' is the definition.
(I've seen this before)
'military volunteers man' is the wordplay.
'military volunteers' becomes 'TA' (Territorial Army, volunteer reserve of UK army).
'man' becomes 'ken' (short for Kenneth).
'ta'+'ken'='TAKEN'
(Other definitions for taken that I've seen before include "Seized" , "Appropriated" , "Stolen; occupied" , "Removed; occupied" , "Charmed" .)