Something to read in the coach (7)
I believe the answer is:
omnibus
'the coach' is the definition.
(synonyms)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for omnibus that I've seen before include "book collection" , "Compound volume" , "Compendium volume" , "Volume containing several books" , "Large volume - public transport" .)