It's on the captain to equip team (7)
I believe the answer is:
armband
'it's on the captain' is the definition.
(eg football captain wearing an armband)
'equip team' is the wordplay.
'equip' becomes 'arm' (arm can mean to equip someone with something).
'team' becomes 'band' (both can mean a group of people).
'arm'+'band'='ARMBAND'
'to' acts as a link.
(Other definitions for armband that I've seen before include "ID worn on sleeve" , "What might hold up sleeve" , "Swimming aid" , "Cloth worn round sleeve" , "It may identify" .)