Source of irritation in Italian church (4)
I believe the answer is:
itch
'source of irritation' is the definition.
(I've seen this before)
'italian church' is the wordplay.
'italian' becomes 'it'.
'church' becomes 'ch' (common abbreviation).
'it'+'ch'='ITCH'
'in' is the link.
(Other definitions for itch that I've seen before include "Irritate" , "Tingle" , "source of irritation" , "great desire" , "Tickle; urge" .)