Uncommon payment for an author (7)

I believe the answer is:

royalty

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

'uncommon payment' is the definition.
'royalty' can be an answer for 'payment' (royalty is a kind of payment). I am not certain of the 'uncommon' bit.

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for royalty that I've seen before include "Member(s) of sovereign family" , "Top people; type of payment" , "Ruler's family" , "percentage earned" , "payment for literary work?" .)

I've seen this clue in The Globe and Mail.

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