Servant, awful brute about 50 (6)
I believe the answer is:
butler
'servant' is the definition.
(butler is a kind of servant)
'awful brute about 50' is the wordplay.
'awful' indicates anagramming the letters.
'about' indicates putting letters inside.
'50' becomes 'l' (roman numeral).
'brute' with letters rearranged gives 'buter'.
'buter' enclosing 'l' is 'BUTLER'.
(Other definitions for butler that I've seen before include "Top servant in posh household" , "Chief male household servant" , "Head male servant" , "Senior servant of a household" , "in charge of port?" .)