One small Church starts in India’s Andaman Island (6)
I believe the answer is:
ischia
'island' is the definition.
(Italian island)
'one small church starts in india's andaman' is the wordplay.
'one' becomes 'I' (Roman numeral).
'small' becomes 's' (abbreviation - e.g. clothes size).
'church' becomes 'ch' (common abbreviation).
'starts in' suggests taking the first letters.
The initial letters of 'india andaman' is 'ia'.
'i'+'s'+'ch'+'ia'='ISCHIA'
(Other definitions for ischia that I've seen before include "Home of islander" , "Italian island" , "Heavily populated island in the Gulf of Naples" , "bits of hipbone" , "Parts of pelvis; isle near Naples" .)