Crossword Genius

Since start of Cup Final a ‘new' heartless City's domination (10)

Ross

I believe the answer is:

ascendancy

I'm a little stuck... Click here to teach me more about this clue!

'domination' is the definition.
(I've seen this before)

'since start of cup final a new heartless city's' is the wordplay.
I cannot quite see how this works, but
'since' could be 'as' (both can mean 'because') and 'as' is found in the answer.
'final' could be 'end' (synonyms) and 'end' is located in the answer.
'a' could be 'an' and 'an' is found in the answer.
This explanation may well be incorrect...

Can you help me to learn more?

(Other definitions for ascendancy that I've seen before include "Influential position" , "Dominating influence (A, not E)" , "Candy canes (anag.)" , "upper hand" , "Domination" .)

I've seen this clue in The Guardian.
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