Coach - or coaches (5)
I believe the answer is:
train
'coaches' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for train that I've seen before include "Railway engine" , "Teach (someone) a skill" , "Rail service" , "union's lengthy item" , "Number of eg carriages in a line" .)