Fellow lawyer Conservative required (9)
I believe the answer is:
mandatory
'required' is the definition.
('mandatory' can be a synonym of 'required')
'fellow lawyer conservative' is the wordplay.
'fellow' becomes 'man' (I've seen this before).
'lawyer' becomes 'da' (D.A. is an example).
'conservative' becomes 'tory' (I've seen this before).
'man'+'da'+'tory'='MANDATORY'
(Other definitions for mandatory that I've seen before include "Obligatory" , "allowing no option" , "required" , "Not optional" , "Compulsory" .)