Rook on cheese plant (5)
I believe the answer is:
brier
'plant' is the definition.
(brier is a kind of plant)
'rook on cheese' is the wordplay.
'rook' becomes 'r' (abbreviation in chess).
'on' means one lot of letters go next to another.
'cheese' becomes 'brie' (Brie is an example**).
'r' after 'brie' is 'BRIER'.
(Other definitions for brier that I've seen before include "It may be smoked" , "plant" , "Thorny bush like the wild rose" , "Prickly shrub" , "smoking pipe" .)