Servant's goodbye coming with retirement finally (5)
I believe the answer is:
valet
'servant's' is the definition.
(valet is a kind of servant)
'goodbye coming with retirement finally' is the wordplay.
'goodbye' becomes 'vale' (farewell in Latin).
'coming with' says to put letters next to each other.
'finally' indicates one should take the final letters.
The final letter of 'retirement' is 't'.
'vale'+'t'='VALET'
(Other definitions for valet that I've seen before include "Man's man" , "Personal servant" , "Clean (a car); attendant" , "Personal serving man" , "Man's manservant" .)