Coach or train (6)
I believe the answer is:
school
I believe this clue is a double definition.
'coach' is the first definition.
(I've seen this before)
'train' is the second definition.
(I've seen this before)
'or' acts as a link.
(Other definitions for school that I've seen before include "some bass?" , "A number of swimmers joined" , "College" , "Sect, faction" , "A number of fish" .)