Islanders keeping band in headquarters (8)
I believe the answer is:
balinese
'islanders' is the definition.
(people from Bali in Indonesia)
'band in headquarters' is the wordplay.
'band' becomes 'line'.
'in' is an insertion indicator.
'headquarters' becomes 'base' (I've seen this before).
'line' put into 'base' is 'BALINESE'.
'keeping' acts as a link.
(Other definitions for balinese that I've seen before include "policy needs external support" , "Islanders" , "Indonesian" , "Foreign language" , "Asian language" .)