Run into street? Careful! (4)
I believe the answer is:
Here is my best explanation:
'careful' is the definition.
('wary' can be similar in meaning to 'careful')
'run into street?' is the subsidiary indication.
'run' becomes 'r' (cricket abbreviation).
'into' is an insertion indicator.
'street?' becomes 'way' (street is a kind of way).
'r' going inside 'way' is 'wary'.
(Other definitions for wary that I've seen before include "Watchful", "Circumspect", "Suspicious", "Cautious - vigilant", "James Bond villain", "Cautious of danger", "Cautious and vigilant.17 Add up for infant", "Distrustful", "Cautious, suspicious" and "Guarded".)