The old magistrate could follow a point (4)
I believe the answer is:
doge
'the old magistrate' is the definition.
(as in the Doges of Venice)
'follow a point' is the wordplay.
'follow' becomes 'dog' (dog can mean to follow or torment).
'a point' becomes 'e' (compass point).
'dog'+'e'='DOGE'
'could' acts as a link.
(Other definitions for doge that I've seen before include "Venetian leader" , "Magistrate of 14 (historical)" , "Venetian chief magistrate" , "foreign magistrate" , "Historically, the chief magistrate of Venice or Genoa" .)