Required that one rang on behalf of (6,3)
I believe the answer is:
called for
'required' is the definition.
('call for' can be a synonym of 'require')
'one rang on behalf of' is the wordplay.
'one rang' becomes 'called' (I've seen this in another clue).
'on behalf of' becomes 'for' (eg speaking on behalf of or for someone else).
'called'+'for'='CALLED-FOR'
'that' acts as a link.
(Other definitions for called for that I've seen before include "Justified" , "summoned" .)