Fat Scottish landowner abandoning island (4)
I believe the answer is:
lard
'fat' is the definition.
(lard is a kind of fat)
'scottish landowner abandoning island' is the wordplay.
'scottish landowner' becomes 'laird' (I've seen this in another clue).
'abandoning' suggests deleting specific letters.
'island' becomes 'i' (geographical abbreviation).
'laird' with 'i' taken out is 'LARD'.
(Other definitions for lard that I've seen before include "Pig's fat" , "Hard cooking fat" , "F [FAT]" , "Pork fat" , "Soft white semisolid fat" .)