Legislator with master’s degree wearing carmine robe, principally (8)
I believe the answer is:
lawmaker
'legislator' is the definition.
(legislators make laws)
'with master's degree wearing carmine robe principally' is the wordplay.
'with' becomes 'w' (abbreviation).
'master's degree' becomes 'MA' (MA is an example).
'wearing' means one lot of letters goes inside another.
'carmine' becomes 'lake' (both refer to a shade of red).
'principally' suggests taking the first letters.
The first letter of 'robe' is 'r'.
'w'+'ma'='wma'
'wma' put within 'lake' is 'lawmake'.
'lawmake'+'r'='LAWMAKER'
(Other definitions for lawmaker that I've seen before include "Sod, possibly" , "Legislator" , "sitting in Parliament?" .)