Old archbishop’s demands for payment, with thank you note (7)
I believe the answer is:
dunstan
'old archbishop's' is the definition.
'dunstan' can be an answer for 'archbishop's' (I have seen 'Former archbishop' mean 'dunstan' so perhaps 'archbishop' could also mean 'dunstan'). I'm not sure about the 'old' bit.
'demands for payment with thank you note' is the wordplay.
'demands for payment' becomes 'duns' (I've seen this in another clue).
'with' says to put letters next to each other.
'thank you' becomes 'ta' (informal way of saying thank you).
'note' becomes 'n' (abbreviation).
'duns'+'ta'+'n'='DUNSTAN'
Can you help me to learn more?
(Other definitions for dunstan that I've seen before include "Saint, tweaked Devil's nose" , "Former archbishop" .)