Given marks for having been observant (7)

I believe the answer is:

spotted

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'given marks' is the definition.
The definition and answer can be both related to change as well as being past participle verbs.
Perhaps you can see a link between them that I don't see?

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for spotted that I've seen before include "As Dick may be" , "Observed" , "Dappled - saw" , "Noticed" , "Saw; mottled" .)

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

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