A lot of a certain breed of cat, appropriately, unknown (4)
I believe the answer is:
many
'a lot of' is the definition.
(many means a lot)
'a certain breed of cat appropriately unknown' is the wordplay.
I cannot really understand how this works, but
'unknown' could be 'y' (algebra) and 'y' is found in the answer.
The remaining letters 'man' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for many that I've seen before include "Multitudinous" , "A great number" , "multitude" , "legion" , "Several" .)