Bristle in grass of well-trimmed lawns (3)
I believe the answer is:
awn
'bristle' is the definition.
(botanical term)
'trimmed lawns' is the wordplay.
'trimmed' means to look at the middle letters (the external letters are trimmed from the word).
The centre of 'lawns' is 'AWN'.
'in grass of well' acts as a link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for awn that I've seen before include "Bristly head of barley sheath, quite wan" , "Bristle-like appendage on grass" , "Beard growing from an ear of barley or rye" , "Stiff bristle on grasses" , "bit of cereal" .)