A slick type, but shy about what's debatable (7)

I believe the answer is:

smoothy

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'type but shy about what's debatable' is the definition.
I don't know anything about this answer so I cannot tell whether this works.

'a slick' is the wordplay.
I cannot really understand how this works, but
'slick' could be 'smooth' (similar in meaning) and 'smooth' is present in the answer.
A single letter 'y' remains which might be clued in a way I don't understand.
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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