Worker purchasing grass before hard race (8)
I believe the answer is:
marathon
'race' is the definition.
(I know that marathon is a type of race)
'worker purchasing grass before hard' is the wordplay.
'worker' becomes 'man' (man is a kind of worker).
'purchasing' means one lot of letters goes inside another (some letters take possession of others).
'grass' becomes 'rat' (both can mean a snitch or informer).
'before hard' becomes 'ho' (I can't explain this - if you can you should believe this answer much more).
'rat'+'ho'='ratho'
'man' placed around 'ratho' is 'MARATHON'.
Can you help me to learn more?
(Other definitions for marathon that I've seen before include "Race of about 26 miles" , "The longest foot-race" , "Race; battle" , "Long-distance running event" , "Footrace of 26 miles 385 yards" .)