Reserve copy (4)
I believe the answer is:
book
This clue could be a double definition.
'reserve' is the first definition.
(synonyms)
'copy' is the second definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe you can see an association between them that I can't see?
Can you help me to learn more?
(Other definitions for book that I've seen before include "See 1 ac" , "Reserve - something to read" , "Quick work" , "Leaves, bound" , "Tome, volume" .)