He left by public transport, getting measure of grain (6)
I believe the answer is:
bushel
'measure of grain' is the definition.
(I've seen this before)
'he left by public transport' is the wordplay.
'left' becomes 'l' (common abbreviation).
'by' says to put letters next to each other.
'public transport' becomes 'bus' (bus is a kind of public transport).
'he'+'l'='hel'
'hel' put after 'bus' is 'BUSHEL'.
'getting' is the link.
(Other definitions for bushel that I've seen before include "Obsolete measure (equal to 8 gallons)" , "Measure equalling eight Imperial gallons" , "Old measure of capacity" , "'Don't hide your light behind a . . . . . .'" , "Unit of dry or liquid measure" .)