Not many? What a relief, I'd say (3)
I believe the answer is:
few
'not many?' is the definition.
('few' is the opposite to 'many')
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for few that I've seen before include "Hardly anyone" , "Considerable number, ironically" , "Indefinite small amount" , "Not many, just a handful" , "Only one or two" .)