Cutter of large bristle — and second used to be cut (9)
I believe the answer is:
lawnmower
'cutter' is the definition.
(I've seen this before)
'large bristle and second used to be cut' is the wordplay.
'large bristle' becomes 'lawn' (I can't explain this - if you can you should give a lot more credence to this answer).
'and' says to put letters next to each other.
'second' becomes 'mo' (both are short periods of time).
'used to be' becomes 'were' (I've seen this before).
'cut' means to remove the last letter.
'were' with its final letter taken off is 'wer'.
'lawn'+'mo'+'wer'='LAWNMOWER'
'of' acts as a link.
(Other definitions for lawnmower that I've seen before include "cutting equipment" , "Grass-cutter" , "It has blades for cutting blades!" , "Grass cutter" .)