Religious adherent adopted by Irish in Dublin (5)
I believe the answer is:
hindu
'religious adherent' is the definition.
(I've seen this before)
'adopted by irish in dublin' is the wordplay.
'adopted by' indicates the answer is hidden within the clue.
'HINDU' is hidden in the letters of 'irish in dublin'.
(Other definitions for hindu that I've seen before include "Person with faith" , "Adherent to dominant religion of India" , "religious type" , "Member of great Indian religion with belief in reincarnation" , "One practising an Indian religion" .)