Running mobile home into grass (10)
I believe the answer is:
scampering
'running' is the definition.
(scampering is a kind of running)
'mobile home into grass' is the wordplay.
'mobile home' becomes 'camper' ('camper' can be a synonym of 'mobile home').
'into' means one lot of letters goes inside another.
'grass' becomes 'sing' (I've seen this in other clues).
'camper' placed within 'sing' is 'SCAMPERING'.
(Other definitions for scampering that I've seen before include "in a hurry" , "Rushing" .)