Conservative on track in Bow Street? (8)
I believe the answer is:
crescent
'bow street?' is the definition.
(street with a curve or 'bow')
'conservative on track' is the wordplay.
'conservative' becomes 'C' (UK political abbreviation).
'on' becomes 're' ('on' can be mean 'with reference to').
'track' becomes 'scent' (both can mean a trace left by someone).
'c'+'re'+'scent'='CRESCENT'
'in' is the link.
(Other definitions for crescent that I've seen before include "Moon shape; curved street" , "Curved shape of the moon in first quarter" , "Turkish emblem" , "Semi-circular shape" , "Curved aspect of the moon" .)