Sailor's left pig covered in fat (8)
I believe the answer is:
larboard
'sailor's left' is the definition.
(I've seen this before)
'pig covered in fat' is the wordplay.
'pig' becomes 'boar' (male pig).
'covered in' indicates putting letters inside.
'fat' becomes 'lard' (lard is a kind of fat).
'boar' placed within 'lard' is 'LARBOARD'.
(Other definitions for larboard that I've seen before include "Port; labrador (anag.)" , "Port side" , "Left side of ship" , "left at sea" , "Sailor's left" .)