Possibly exclusive prefix, in no way positive (3)
I believe the answer is:
non
'positive' is the definition.
Both the definition and answer are adjectives. Maybe you can see a link between them that I don't see?
'possibly exclusive prefix in no way' is the wordplay.
'possibly exclusive prefix in' becomes 'n' (I can't explain this - if you can you should believe this answer much more).
'no' becomes 'o' (resembles 0 - 'no' can mean 'zero').
'way' becomes 'n' (Compass direction - North).
'n'+'o'+'n'='NON'
Can you help me to learn more?
(Other definitions for non that I've seen before include "Prefixed negation of a word" , "Combining form meaning not" , "- - -stick" , "Prefix meaning negative" , "Prefix meaning not or none" .)