Run into street? Careful! (4)
I believe the answer is:
wary
'careful' is the definition.
('wary' can be similar in meaning to 'careful')
'run into street?' is the wordplay.
'run' becomes 'r' (cricket abbreviation).
'into' indicates putting letters inside.
'street?' becomes 'way' (street is a kind of way).
'r' inserted inside 'way' is 'WARY'.
(Other definitions for wary that I've seen before include "Watchful" , "Guarded" , "Circumspect" , "Cautious - vigilant" , "James Bond villain" .)