Mrs Mopp is old lady making personal appeal (8)
I believe the answer is:
charisma
'personal appeal' is the definition.
('charisma' can be a synonym of 'personal appeal')
'mrs mopp is old lady' is the wordplay.
'mrs mopp' becomes 'char' (I've seen this before).
'old lady' becomes 'ma'.
'char'+'is'+'ma'='CHARISMA'
'making' is the link.
(Other definitions for charisma that I've seen before include "Compelling attractiveness" , "divinely conferred talent?" , "Pull" , "power to influence" , "quality inspiring devotion" .)