Monkey wrenches some off in exchange (8)

I believe the answer is:

marmoset

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'monkey wrenches' is the definition.
'marmoset' can be an answer for 'monkey' (I've seen this before). I'm not sure about the 'wrenches' bit.

'some off in exchange' is the wordplay.
'off' is an anagram indicator.
'in' means one lot of letters goes inside another.
'exchange' becomes 'mart' (I can't justify this - if you can you should believe this answer much more).
'some' anagrammed gives 'mose'.
'mose' inserted into 'mart' is 'MARMOSET'.

Can you help me to learn more?

(Other definitions for marmoset that I've seen before include "Turn morse mat over for the monkey" , "Small South American monkey" , "Star memo about kind of monkey" , "Small New World monkey" , "Primate" .)

I've seen this clue in the Sydney Morning Herald.

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