This may be quite an old thing (7)
I believe the answer is:
antique
'old thing' is the definition.
The answer and definition 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?
'this may be quite an' is the wordplay.
'this may be' indicates anagramming the letters.
'quite'+'an'='quitean'
'quitean' is an anagram of 'ANTIQUE'.
Can you help me to learn more?
(Other definitions for antique that I've seen before include "describing Shelley's traveller's land" , "Old-fashioned, outdated" , "Very old and possibly valuable" , "Ancient object" , "Old collectable object" .)