Every coach beginning to leave (4)
I believe the answer is:
each
'every' is the definition.
(synonyms)
'coach beginning to leave' is the wordplay.
'coach' becomes 'teach' (I've seen this before).
'beginning to leave' means to remove the first letter.
'teach' with its initial letter taken off is 'EACH'.
(Other definitions for each that I've seen before include "every one of a group" , "Every single one, person or thing" , "Singly, per capita" , "Every one of a number" , "...per head" .)