Is it one's job to make class distinctions? (6)

I believe the answer is:

sorter

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'is it one's job to' is the definition.
I can't judge whether this definition defines the answer.

'class distinctions?' is the wordplay.
'class' becomes 'sort' (synonyms).
'distinctions?' becomes 'er' (I can't justify this - if you can you should give a lot more credence to this answer).
'sort'+'er'='SORTER'

'make' acts as a link.

Can you help me to learn more?

I've seen this clue in the Evening Standard.

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