Pure manoeuvring, to cross street in the morning against the flow (8)
I believe the answer is:
upstream
'against the flow' is the definition.
(I've seen this before)
'pure manoeuvring to cross street in the morning' is the wordplay.
'manoeuvring' indicates anagramming the letters.
'to cross' means one lot of letters goes inside another.
'street' becomes 'st'.
'in the morning' becomes 'am'.
'pure' with letters rearranged gives 'upre'.
'upre' enclosing 'st' is 'upstre'.
'upstre'+'am'='UPSTREAM'
(Other definitions for upstream that I've seen before include "contraflow" , "away from estuary?" , "Eats rump (anag)" , "Against a river's natural flow" , "opposing current tendencies" .)