In the Irish Republic, the New Testament is unabridged (6)
I believe the answer is:
entire
'unabridged' is the definition.
(I've seen this in another clue)
'in the irish republic the new testament' is the wordplay.
'in the' means one lot of letters goes inside another.
'irish republic' becomes 'eire' (synonyms).
'the new testament' becomes 'nt'.
'eire' enclosing 'nt' is 'ENTIRE'.
'is' is the link.
(Other definitions for entire that I've seen before include "Lure" , "outright" , "Whole; unbroken" , "Complete, intact" , "Full, intact" .)