Bummer (3,4)
There are a few possibilities for this:
low note
(Other definitions for rats that I've seen before include "(Hunts) rodents - expression of irritation" , "Heels" , "Treacherous rodents" , "Mild oath - sewer residents" , "First word of 'The 21 19'" .)
'bummer' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for drag that I've seen before include "woman's attire" , "Women's clothes worn by a man - pull" , "car" , "Trail; bore" , "Yank" .)