One of many in some gallery? (5)
I believe the answer is:
miner
'one' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'many in some gallery?' is the wordplay.
'many in' becomes 'mine' (I can't explain this - if you can you should believe this answer much more).
'some' indicates the central letters.
'gallery?' becomes 'art' (synonyms).
The middle of 'art' is 'r'.
'mine'+'r'='MINER'
'of' acts as a link.
Can you help me to learn more?
(Other definitions for miner that I've seen before include "Underground worker" , "Pitman" , "One who digs for ore" , "Man of 49" , "it's the pits, for me" .)