Follow the old lady's belief (5)
I believe the answer is:
dogma
'belief' is the definition.
(dogma is a kind of belief)
'follow the old lady's' is the wordplay.
'follow' becomes 'dog' (dog can mean to follow or torment).
'the old lady' becomes 'ma' (both can informally mean mother).
'dog'+'ma'='DOGMA'
(Other definitions for dogma that I've seen before include "Blind faith required" , "Body of religious doctrine" , "fixed opinion" , "Body of creed" , "Inflexible doctrine" .)