A saint rung by a biddy (7)
I believe the answer is:
stephen
'a saint' is the definition.
(St Stephen)
'rung by a biddy' is the wordplay.
'rung' becomes 'step' (I've seen this before).
'by' is a charade indicator (letters next to each other).
'a biddy' becomes 'hen' ('hen' can be a synonym of 'biddy').
'step'+'hen'='STEPHEN'
(Other definitions for stephen that I've seen before include "Boxing Day saint" , "First Christian martyr" , "He's commemorated on December 26th" , "-- Fry; -- Hawking" , "-- Hawking, English physicist" .)