Republican ain’t travelling with queen in coach! (7)
I believe the answer is:
trainer
'coach' is the definition.
(as in a sports coach)
'republican ain't travelling with queen' is the wordplay.
'republican' becomes 'R' (abbreviation in US politics).
'travelling' is an anagram indicator.
'with' says to put letters next to each other.
'queen' becomes 'ER' (abbreviation for Elizabeth Regina).
'r'+'aint'='raint'
'raint' with letters rearranged gives 'train'.
'train'+'er'='TRAINER'
'in' acts as a link.
(Other definitions for trainer that I've seen before include "Soft shoe; simulator" , "Sports instructor" , "Sports shoe" , "Sports coach" , "Plimsoll or sneaker" .)