Damn vermin (4)
I believe the answer is:
rats
This clue is a double definition.
'damn' is the first definition.
(both are expressions of annoyance)
'vermin' is the second definition.
(I've seen this before)
(Other definitions for rats that I've seen before include "First word of 'The 21 19'" , "were piped away" , "Rodent pests" , "Treacherous rodents" , "Hamelin's pests" .)