Brief obstruction when crossing street (9)
I believe the answer is:
barrister
'brief' is the definition.
(brief can mean a lawyer)
'obstruction when crossing street' is the wordplay.
'obstruction' becomes 'barrier' (barrier is a kind of obstruction).
'when crossing' means one lot of letters goes inside another.
'street' becomes 'st' (abbreviation).
'barrier' placed around 'st' is 'BARRISTER'.
(Other definitions for barrister that I've seen before include "Lawyer for the higher courts" , "Court lawyer" , "One represents clients in court" , "Rarest rib for the eminent lawyer" , "American lawyer" .)