Blue Berets’ former muscle man not bargained for (10)
I believe the answer is:
unexpected
'not bargained for' is the definition.
'blue berets' former muscle man' is the wordplay.
I cannot quite understand how this works, but
'former' could be 'ex' and 'ex' is located in the answer.
'muscle' could be 'pec' (I've seen this in other clues) and 'pec' is found in the answer.
'man' could be 'ted' (Ted is a man's name) and 'ted' is present in the answer.
The remaining letters 'un' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
(Other definitions for unexpected that I've seen before include "Unforeseen" , "Surprising" , "Not foreseen" .)