Former coach's conscientious commitment (9)
I believe the answer is:
diligence
This clue is a double definition.
'former coach's' is the first definition.
(diligence was a historical type of stagecoach)
'conscientious commitment' is the second definition.
(eg commitment to a task)
(Other definitions for diligence that I've seen before include "Painstaking care" , "hard effort" , "that could be due?" , "Industriousness" , "Careful and persistent work or effort" .)