Atmosphere about street is bustling (5)
I believe the answer is:
astir
'bustling' is the definition.
(I've seen this in another clue)
'atmosphere about street' is the wordplay.
'atmosphere' becomes 'air' (synonyms).
'about' is an insertion indicator.
'street' becomes 'st' (abbreviation).
'air' placed around 'st' is 'ASTIR'.
'is' acts as a link.
(Other definitions for astir that I've seen before include "Up and about -- is art (anag)" , "In motion - out of bed" , "Awake and out of bed" , "in the land of the living" , "In a state of movement" .)