What suggests Mother Superior's part of London (7)

'what suggests mother superior's' is the definition.
I know nothing about this answer so I can't tell whether this works.

'part of london' is the wordplay.
I cannot quite see how this works, but
'part' could be 'head' (head is a kind of part) and 'head' is present in the answer.
The remaining letters 'nun' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?