Lop heads off plant (8)
I believe the answer is:
asphodel
'plant' is the definition.
The answer is an example.
'lop heads off' is the wordplay.
'off' indicates an anagram.
'lop'+'heads'='lopheads'
'lopheads' with letters rearranged gives 'ASPHODEL'.
(Other definitions for asphodel that I've seen before include "Old shape (anag) - plant" , "Shop deal (anag.)" , "Lily-like plant, the flower of death to ancient Greeks" , "liliaceous plant" , "Plant of lily family - lop heads (anag)" .)