He may well hope to make a profit on the stock market (6)
I believe the answer is:
farmer
'he may well hope to make a profit on the stock market' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'he may well' is the wordplay.
'he' becomes 'Far'.
'may well' becomes 'mer' (I can't explain this - if you can you should believe this answer much more).
'far'+'mer'='FARMER'
Can you help me to learn more?
(Other definitions for farmer that I've seen before include "Tender of crops/stock" , "He lives off the land" , "Agriculturalist" , "Smallholder, e.g." , "Food producer" .)