Monkey business is done here including some that's criminal (8)
I believe the answer is:
marmoset
'monkey business' is the definition.
'marmoset' can be an answer for 'monkey' (I've seen this before). I am not sure about the 'business' bit.
'done here including some that's criminal' is the wordplay.
'done here' becomes 'mart' (I can't explain this - if you can you should give a lot more credence to this answer).
'including' is an insertion indicator.
'that's criminal' is an anagram indicator.
'some' anagrammed gives 'mose'.
'mart' going around 'mose' is 'MARMOSET'.
'is' acts as a link.
Can you help me to learn more?
(Other definitions for marmoset that I've seen before include "Somme rat? (anag)" , "Take me to arms about bushy-tailed monkey of tropical America" , "Small bushy-tailed monkey" , "Small tropical American monkey" , "Small New World monkey" .)