Cut top off grass or bristle (3)
I believe the answer is:
awn
'bristle' is the definition.
(botanical term)
'cut top off grass' is the wordplay.
'cut top off' means to remove the first letter.
'grass' becomes 'lawn' (a lawn is an area of grass).
'lawn' with its initial letter taken off is 'AWN'.
'or' is the link.
(Other definitions for awn that I've seen before include "Bristly head of barley sheath, quite wan" , "Bristly growth" , "Bristle on cereal spike" , "Beard of cereal" , "Beard of plant" .)