Crossword Genius

Just two terribly? (8)

Ross

I believe the answer is:

deucedly

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

'terribly?' is the definition.
(thesaurus)

'just two' is the wordplay.
I cannot quite understand how this works, but
'two' could be 'deuce' (synonyms) and 'deuce' is found in the answer.
This explanation may well be incorrect...

Can you help me to learn more?

I've seen this clue in the Evening Standard.
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