Spy on street is Harry (6)
I believe the answer is:
molest
'is harry' is the definition.
(I've seen this before)
'spy on street' is the wordplay.
'spy' becomes 'mole' (mole is a kind of spy).
'on' is a charade indicator (letters next to each other).
'street' becomes 'st' (abbreviation).
'mole'+'st'='MOLEST'
(Other definitions for molest that I've seen before include "Maliciously interfere with" , "Attack or interfere with a person" , "Plague" , "Paw" , "Pester; assault" .)