Once more street is opposed (7)
I believe the answer is:
against
'is opposed' is the definition.
(I've seen this in another clue)
'once more street' is the wordplay.
'once more' becomes 'again' (synonyms).
'street' becomes 'st' (abbreviation).
'again'+'st'='AGAINST'
(Other definitions for against that I've seen before include "antagonistic" , "Not supporting" , "In contrast to; touching" , "close by" , "Facing" .)