Supervisor in military office? (6)
I believe the answer is:
warden
'supervisor' is the definition.
(I've seen this before)
'military office?' is the wordplay.
'military' becomes 'war' (relating to war or the military).
'office?' becomes 'den' (I've seen this in other clues).
'war'+'den'='WARDEN'
'in' acts as a link.
(Other definitions for warden that I've seen before include "Custodian" , "Person in charge (of traffic etc)" , "Chief official in charge of a prison" , "Caretaker" , "Warned about supervisory official" .)