Sound in street restricted by regulation (6)
I believe the answer is:
rustle
'sound' is the definition.
(rustle is a kind of sound)
'street restricted by regulation' is the wordplay.
'street' becomes 'st'.
'restricted by' indicates putting letters inside (I've seen this in other clues).
'regulation' becomes 'rule' ('rule' can be a synonym of 'regulation').
'st' put inside 'rule' is 'RUSTLE'.
'in' is the link.
(Other definitions for rustle that I've seen before include "Dry crackling sound" , "Steal cattle or livestock with whispering sound" , "making little noise" , "Steal cattle in the old West" , "Swish - steal cattle" .)