A discarded cigarette-holder (7)
I believe the answer is:
ashtray
'a discarded cigarette-holder' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps there's an association between them I don't understand?
This is all the clue.
Can you help me to learn more?
(Other definitions for ashtray that I've seen before include "Smelly receptacle" , "debris receptacle" , "Receptacle for cigarette butts" , "Receptacle for tobacco detritus" , "Smoker's receptacle" .)