Pub losing heart with every violation (6)
I believe the answer is:
breach
'violation' is the definition.
(I've seen this before)
'pub losing heart with every' is the wordplay.
'pub' becomes 'bar' (both are drinking establishments).
'losing heart' means to remove the middle letters.
'with' means one lot of letters go next to another.
'every' becomes 'each' (synonyms).
'bar' with its centre removed is 'br'.
'br'+'each'='BREACH'
(Other definitions for breach that I've seen before include "Opening -- infraction" , "Open up" , "Fissure" , "Gap (in defensive wall)" , "Violation, maybe of the peace" .)