Run miles by river outside of town (10)
I believe the answer is:
extramural
'outside of town' is the definition.
(extramural means outside the walls of a settlement)
'run miles by river' is the wordplay.
'run' becomes 'extra' (cricket run).
'miles' becomes 'm' (common abbreviation).
'by river' becomes 'ural' (Russian river. I am not sure about the 'by' bit.).
'extra'+'m'+'ural'='EXTRAMURAL'
(Other definitions for extramural that I've seen before include "outside the university" , "outside city limits" , "Off-premises (univ. studies)" , "Not on course" , "What may be a wide painting" .)