Unwanted stuff: jam set badly (6)
I believe the answer is:
jetsam
'unwanted stuff' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe you can see a link between them that I can't see?
'jam set badly' is the wordplay.
'badly' indicates an anagram.
'jam'+'set'='jamset'
'jamset' with letters rearranged gives 'JETSAM'.
Can you help me to learn more?
(Other definitions for jetsam that I've seen before include "Items thrown overboard" , "Cargo cast overboard" , "Floating wreckage" , "Material flung overboard" , "lost cargo" .)