Bristle Labour leader removed from grassy area (3)
I believe the answer is:
awn
'bristle' is the definition.
(botanical term)
'labour leader removed from grassy area' is the wordplay.
'labour leader' becomes 'l' (the leading letter of 'labour').
'removed from' is a deletion indicator.
'grassy area' becomes 'lawn' (I've seen this in another clue).
'lawn' with 'l' taken out is 'AWN'.
(Other definitions for awn that I've seen before include "Bristle in flowering part of some grasses" , "bit of cereal" , "Stiff bristle on grasses" , "Bristle on, eg, barley" , "Beard of plant" .)