Servant, new trainee, butler ultimately (8)
I believe the answer is:
retainer
'servant' is the definition.
('retainer' can be a synonym of 'servant')
'new trainee butler ultimately' is the wordplay.
'new' indicates an anagram.
'ultimately' indicates one should take the final letters.
The last letter of 'butler' is 'r'.
'trainee' is an anagram of 'retaine'.
'retaine'+'r'='RETAINER'
(Other definitions for retainer that I've seen before include "Old servant - preliminary fee" , "Old servant - fee paid in advance" , "Down-payment for Eritrean" , "money to be paid in advance" , "Part payment down for an old servant" .)