Shifts hell for old servant (8)
I believe the answer is:
turnspit
'old servant' is the definition.
(historical servant who turned meat on a spit)
'shifts hell' is the wordplay.
'shifts' becomes 'turns' (turn is a kind of shift).
'hell' becomes 'pit' ('the pit' can mean hell).
'turns'+'pit'='TURNSPIT'
'for' acts as a link.
(Other definitions for turnspit that I've seen before include "You have rotisserie" , "Former kitchen servant" , "Old roast attendant" , "Cooking assistant" , "Lowly servant" .)