City that is supportive of new UK leader (4,6)
I believe the answer is:
auld reekie
'supportive of new uk leader' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.
'city that is' is the wordplay.
I cannot quite see how this works, but
'that is' could be 'ie' (short for Latin 'id est', 'that is') and 'ie' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for auld reekie that I've seen before include "Name for Edinburgh" , "Former nickname of Edinburgh, 'old smoky'" .)