Underwear of poor quality (5)
I believe the answer is:
pants
I believe this is a double definition.
'underwear' is the first definition.
(I know that pants is a type of underwear)
'of poor quality' is the second definition.
(it's pants - meaning it's bad)
(Other definitions for pants that I've seen before include "sounds exhausted" , "boxers?" , "Useless (slang) - gasps" , "Rubbish (slang) - undergarment" , "Shorts" .)