Island nation’s singles infiltrating subcontinent (9)
I believe the answer is:
indonesia
'island nation's' is the definition.
'Indonesia' can be an answer for 'nation's' (Indonesia is an example). I'm not sure about the 'island' bit.
'singles infiltrating subcontinent' is the wordplay.
'singles' becomes 'ones' ('one' can be a synonym of 'single').
'infiltrating' indicates putting letters inside.
'subcontinent' becomes 'india' (I've seen this before).
'ones' placed inside 'india' is 'INDONESIA'.
Can you help me to learn more?
(Other definitions for indonesia that I've seen before include "Muslim republic" , "Asian country, capital Jakarta" , "I said none (anag) - country" , "SE Asian country" , "Asian republic" .)