Smart running (7)
I believe the answer is:
dashing
I believe this clue is a double definition.
'smart' is the first definition.
(thesaurus)
'running' is the second definition.
(dashing is a kind of running)
(Other definitions for dashing that I've seen before include "as blade might be" , "Running; stylish" , "Frustrating; debonair" , "Stylish, adventurous" , "Making haste" .)