What rate fixers do? (3,3,4)

I believe the answer is:

set the pace

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'fixers do?' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.

'what rate' is the wordplay.
'what' becomes 'setthe' (I can't justify this - if you can you should believe this answer much more).
'rate' becomes 'pace' (pace is a kind of rate).
'setthe'+'pace'='SET THE PACE'

Can you help me to learn more?

I've seen this clue in The Irish News.

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