Many will disagree with it (3)
I believe the answer is:
few
'many' is the definition.
Both the definition and answer are adjectives. Maybe there's a link between them I don't understand?
'will disagree with it' is the wordplay.
I cannot quite understand how this works, but
'with' could be 'w' (abbreviation) and 'w' is located in the answer.
'it' could be 'e' ('e' can mean 'electronic' which is similar to 'IT') and 'e' is found in the answer.
A single letter 'f' remains which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for few that I've seen before include "Considerable number, ironically" , "'''Many are called but ... are chosen'' (Bible) (3)'" , "Not many, just a handful" , "Indefinite small amount" , "Relatively small number" .)