Swine's unrestrained love confined to pub (4,4)
I believe the answer is:
wild boar
'swine's' is the definition.
(wild boar is a kind of swine)
'unrestrained love confined to pub' is the wordplay.
'unrestrained' becomes 'wild' ('wild' can be a synonym of 'unrestrained').
'love' becomes 'o' (In tennis, 'love' means 'zero').
'confined to' is an insertion indicator.
'pub' becomes 'bar' (I've seen this before).
'o' going inside 'bar' is 'boar'.
'wild'+'boar'='WILD BOAR'
(Other definitions for wild boar that I've seen before include "Feral pig" , "Untamed pig" , "Game" , "Non-domesticated pig" , "strong meat" .)