Run a line? (4)
I believe the answer is:
dash
I believe this clue is a double definition.
'run' is the first definition.
(dashing is a kind of running)
'a line?' is the second definition.
(thesaurus)
(Other definitions for dash that I've seen before include "scotch" , "Hurry ("must ____!")" , "rats" , "Striking" , "Hurry; destroy (hopes)" .)