Fundamental article about the Italian church (8)
I believe the answer is:
basilica
'church' is the definition.
(basilica is a kind of church)
'fundamental article about the italian' is the wordplay.
'fundamental' becomes 'basic' ('basic' can be similar in meaning to 'fundamental'**).
'article' becomes 'a' (indefinite article).
'about' is an insertion indicator.
'the italian' becomes 'il' (the in Italian).
'basic'+'a'='basica'
'basica' enclosing 'il' is 'BASILICA'.
(Other definitions for basilica that I've seen before include "Church or cathedral of high rank" , "Romanesque church" , "Roman law court; church" , "Palatial church" , "Roman-style church" .)