Resident of islands keeping in with islanders initially (4)
I believe the answer is:
kiwi
'resident of islands' is the definition.
'keeping in with islanders initially' is the wordplay.
'initially' suggests taking the first letters.
The initial letters of 'keeping in with islanders' is 'KIWI'.
(Other definitions for kiwi that I've seen before include "Enzedder; flightless bird" , "Someone from Auckland?" , "apteryx" , "Flightless New Zealand bird" , "one with big bill" .)