Mum elevating 2's brother, a new boss (7)
I believe the answer is:
manager
'boss' is the definition.
(I know that boss can be written as manager)
'mum elevating 2's brother a new' is the wordplay.
I cannot really understand how this works, but
'mum' could be 'ma' (ma can mean mother) and 'ma' is located in the answer.
'a' is found in the answer.
'new' could be 'n' (common abbreviation eg NT for New Testament) and 'n' is found in the answer.
This explanation may well be incorrect...
(Other definitions for manager that I've seen before include "Sports team runner" , "Supervisor" , "Coach" , "Someone in control (or who copes?)" , "One in charge of sports team" .)