Impressive understanding has moved husband (8)

I believe the answer is:

emphatic

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'impressive' is the definition.
Both the definition and answer are adjectives. Maybe you can see a link between them that I can't see?

I don't understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for emphatic that I've seen before include "Forceful and definite" , "Forceful in expression" , "In no uncertain terms" , "For sure" , "Categorical" .)

I've seen this clue in The Telegraph.

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