Colleagues make worst mistake (9)
I believe the answer is:
workmates
'colleagues' is the definition.
(I know this)
'make worst mistake' is the wordplay.
'mistake' indicates an anagram.
'make'+'worst'='makeworst'
'makeworst' anagrammed gives 'WORKMATES'.
(Another definition for workmates that I've seen is " Firm friends possibly".)
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