Going ahead in a coach is always an advantage (5)
I believe the answer is:
bonus
'advantage' is the definition.
(I have seen 'The advantage' mean 'bonus' so perhaps 'advantage' could also mean 'bonus')
'going ahead in a coach is always an' is the wordplay.
I cannot quite understand how this works, but
'going' could be 'on' (both can mean functioning or activated) and 'on' is found in the answer.
'coach' could be 'bus' (synonyms) and 'bus' is present in the leftover letters.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for bonus that I've seen before include "Extra payment, may be performance-related" , "Tip" , "Extra money paid on top of salary" , "Something more than you expected" , "Payment additional to the expected or usual" .)