Player in game with Hull City finishes in a threatening manner (7)

I believe the answer is:

blackly

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

'player in game with hull city finishes' is the definition.
I can't judge whether this defines the answer.

'threatening manner' is the wordplay.
'threatening' becomes 'black' (black can mean foreboding).
'manner' becomes 'ly' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'black'+'ly'='BLACKLY'

'in a' is the link.

Can you help me to learn more?

I've seen this clue in The Guardian.

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