Having detected one’s weak point, nagged about it (5,5)

'one's weak point nagged about it' is the definition.
I know nothing about this answer so I can't tell whether this works.

'having detected' is the wordplay.
I cannot really see how this works, but
'detected' could be 'found' ('find' can be a synonym of 'detect') and 'found' is located in the answer.
The remaining letters 'fault' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...

Can you help me to learn more?