Pressure as Balkan approaches unknown man in the street? (6-2)
I believe the answer is:
passer-by
'man in the street?' is the definition.
'pressure as balkan approaches unknown' is the wordplay.
'pressure' becomes 'p' (abbreviation).
'balkan' becomes 'serb'.
'approaches' says to put letters next to each other.
'unknown' becomes 'y' (algebra).
'p'+'as'+'serb'+'y'='PASSER-BY'
(Other definitions for passer-by that I've seen before include "Person walking past" , "Witness" , "One happening past" , "Spectator not stopping?" , "One walking near" .)