Monitor before iron court (7)
I believe the answer is:
prefect
'monitor' is the definition.
(a prefect is a monitor in a school)
'before iron court' is the wordplay.
'before' becomes 'pre' (prefix meaning 'before').
'iron' becomes 'Fe' (Fe is the chemical symbol for iron).
'court' becomes 'ct' (abbreviation used in road names).
'pre'+'fe'+'ct'='PREFECT'
(Other definitions for prefect that I've seen before include "School senior" , "Pupil with authority" , "Student monitor" , "French official and senior pupil" , "School monitor" .)