Warm in Rhode Island, back bitten by insect (8)
I believe the answer is:
'warm' is the definition.
'rhode island back bitten by insect' is the wordplay.
'rhode island' becomes 'ri' (US postal abbreviation).
'back' becomes 'end' (I've seen this in other clues).
'bitten by' indicates putting letters inside (I've seen this in other clues).
'insect' becomes 'fly' (fly is a kind of insect).
'riend' put inside 'fly' is 'FRIENDLY'.
'in' is the link.
(Other definitions for friendly that I've seen before include "Affable" , "match?" , "Sociable" , "Kind, pleasant" , "One is obviously on good terms with" .)