Train workers to be drivers (8)
I believe the answer is:
coachmen
'drivers' is the definition.
(coachman is a kind of driver)
'train workers' is the wordplay.
'train' becomes 'coach' (synonyms).
'workers' becomes 'men' (men can mean staff or employees).
'coach'+'men'='COACHMEN'
'to be' is the link.
(Other definitions for coachmen that I've seen before include "Carriage drivers" , "riders" .)