A Republican blocks European getting early release (6)
I believe the answer is:
parole
'early release' is the definition.
'a republican blocks european' is the wordplay.
'republican' becomes 'r' (abbreviation).
'blocks' means one lot of letters goes inside another (the inside letters form a 'blockage').
'european' becomes 'pole' (Pole is an example).
'a'+'r'='ar'
'ar' inserted into 'pole' is 'PAROLE'.
'getting' is the link.
(Other definitions for parole that I've seen before include "Temporary release (of a prisoner)" , "Provisional release (for prisoner)" , "Conditionally release" , "Give Al rope when he's released early" , "Conditional release from imprisonment" .)