The many reduced by some? (4)
I believe the answer is:
them
'some?' is the definition.
I don't know anything about this answer so I cannot tell whether this works.
'the many reduced by' is the wordplay.
'many reduced' becomes 'm' (Roman numeral for a thousand; 'reduced' indicates an abbreviation).
'by' says to put letters next to each other.
'the'+'m'='THEM'
Can you help me to learn more?
(Other definitions for them that I've seen before include "people objectively" , "Let -- eat cake" , "Certainly not us, the other lot" , "(To/from) those people" , "Those people (as object)" .)