Card players and coach get on board (7)
I believe the answer is:
entrain
'get on board' is the definition.
(I've seen this before)
'card players and coach' is the wordplay.
'card players' becomes 'en' (I am not sure about this - if you are sure you should believe this answer much more).
'and' means one lot of letters go next to another.
'coach' becomes 'train' ('train' can be a synonym of 'coach').
'en'+'train'='ENTRAIN'
Can you help me to learn more?
(Other definitions for entrain that I've seen before include "Put on board at the station" , "Get on a rail service" , "Sweep along" , "Board a rail service" , "Go on board at the station" .)