Making a comeback, ruler takes second Sumerian city (9)
I believe the answer is:
resurgent
'second sumerian city' is the definition.
Both the answer and definition are adjectives. Maybe you can see a link between them that I can't see?
'making a comeback ruler takes' is the wordplay.
'making a comeback' says the letters should be written in reverse.
'ruler' becomes 'ER' (abbreviation for Elizabeth Regina).
'takes' becomes 'surgent' (I can't justify this - if you can you should believe this answer much more).
'er' in reverse letter order is 're'.
're'+'surgent'='RESURGENT'
Can you help me to learn more?
(Other definitions for resurgent that I've seen before include "making comeback" , "Coming back to life" , "Reviving in popularity" , "Reviving after period of inactivity" , "Reviving after a lull" .)