Rats, gnats, and brats (5)
I believe the answer is:
pests
'rats gnats and brats' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for pests that I've seen before include "Take steps to troublesome animal." , "Steps taken about nuisances" , "Persistently annoying persons" , "Steps (anag.)" .)