Conservative lawbreaker ignoring the first leader (5)
I believe the answer is:
chief
'leader' is the definition.
(I know that chief is a type of supervisor)
'conservative lawbreaker ignoring the first' is the wordplay.
'conservative' becomes 'C' (UK political abbreviation).
'lawbreaker' becomes 'thief'.
'ignoring the first' means to remove the first letter.
'thief' with its initial letter taken away is 'hief'.
'c'+'hief'='CHIEF'
(Other definitions for chief that I've seen before include "Boss" , "Head of a native American tribe" , "Tribe leader" , "Person in charge, head" , "Ordinary type" .)