Not involved with many fools (10)
I believe the answer is:
simpletons
'fools' is the definition.
The answer and definition can be both people as well as being plural nouns.
Perhaps there's a link between them I don't understand?
'not involved with many' is the wordplay.
'not involved' becomes 'simple' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'with' says to put letters next to each other.
'many' becomes 'tons' (tons of something).
'simple'+'tons'='SIMPLETONS'
Can you help me to learn more?
(Another definition for simpletons that I've seen is " gulls".)