One who grows very much, only to be reduced by 50% (6)
I believe the answer is:
farmer
'one who grows very much' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'only to be reduced by 50%' is the wordplay.
'only' becomes 'mere' (I've seen this before).
'to be reduced' means to remove the last letter.
'by' is a charade indicator (letters next to each other).
'50%' becomes 'far' (I can't explain this - if you can you should give a lot more credence to this answer).
'mere' with its last letter removed is 'mer'.
'mer' put after 'far' is 'FARMER'.
Can you help me to learn more?
(Other definitions for farmer that I've seen before include "Ranchero" , "Land worker" , "Old MacDonald, for example" , "Food producer" , "Cultivator" .)