Scottish island -- island lacking large plant (4)
I believe the answer is:
tree
'large plant' is the definition.
(I've seen this before)
'scottish island island lacking' is the wordplay.
'scottish island' becomes 'tiree' (island of the Inner Hebrides).
'island' becomes 'i'.
'lacking' suggests deleting specific letters.
'tiree' with 'i' taken out is 'TREE'.
(Other definitions for tree that I've seen before include "Eg, laburnum" , "famous actor" , "Genealogist's graphic" , "Branching diagram" , "Hazel for instance" .)