Evidence of authority to issue weapons to troop (7)
I believe the answer is:
armband
'evidence of authority' is the definition.
(some sports captains wear armbands)
'issue weapons to troop' is the wordplay.
'issue weapons to' becomes 'arm'.
'troop' becomes 'band' (I've seen this before).
'arm'+'band'='ARMBAND'
'to' acts as a link.
(Other definitions for armband that I've seen before include "Circlet worn on sleeve" , "form of identification" , "Inflatable aid for those learning to swim" , "It may identify" , "Loop for holding up a shirtsleeve" .)