Left pig covered in fat (8)
I believe the answer is:
larboard
'left' is the definition.
(synonyms)
'pig covered in fat' is the wordplay.
'pig' becomes 'boar' (I've seen this before).
'covered in' is an insertion indicator.
'fat' becomes 'lard' (lard is a kind of fat).
'boar' inserted within 'lard' is 'LARBOARD'.
(Other definitions for larboard that I've seen before include "Port; labrador (anag.)" , "Side of ship for Labrador" , "Old term for port (naut.)" , "Left side of ship" , "left at sea" .)