Geordie mother dined with one in Muslim leader’s office (7)
I believe the answer is:
imamate
'muslim leader's office' is the definition.
(I've seen this before)
'geordie mother dined with one' is the wordplay.
'geordie mother' becomes 'mam' (Geordie or Newcastle version of 'mum').
'dined' becomes 'ate' (I've seen this in another clue).
'with' says to put letters next to each other.
'one' becomes 'i' (Roman numeral).
'mam'+'ate'='mamate'
'mamate' put after 'i' is 'IMAMATE'.
'in' acts as a link.
(Other definitions for imamate that I've seen before include "Prayer leader's office" , "position of Muslim leader" , "Muslim leader's office" , "cleric's office" , "Islamic country" .)