Pull small coach (6)
I believe the answer is:
strain
'pull' is the definition.
(I've seen this before)
'small coach' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'coach' becomes 'train' (both can mean to instruct a sportsperson).
's'+'train'='STRAIN'
(Other definitions for strain that I've seen before include "Family; effort" , "Injure (a muscle); distinct breed" , "Muscle injury - tension" , "Pressure - filter" , "song" .)