Walk or run on street (6)
I believe the answer is:
Here is my best explanation:
'walk' is the definition.
(stroll is a kind of walk)
'run on street' is the subsidiary indication.
'run' becomes 'roll' (rolling is a kind of running**).
'on' says to put letters next to each other.
'street' becomes 'st'.
'roll' put after 'st' is 'stroll'.
'or' is the link.
(Other definitions for stroll that I've seen before include "Pleasant walk", "A casual or leisurely walk", "Constitutional", "swan", "Walk casually", "gentle walk", "Promenade", "Saunter in no particular direction", "A pleasant and leisurely walk" and "A casual or lazy walk".)