Adapt firearm removed from its case (6)

I believe the answer is:

evolve

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'adapt' is the definition.
The definition and answer can be both related to change as well as being verbs in their base form.
Perhaps you can see a link between them that I don't see?

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

Can you help me to learn more?

(Other definitions for evolve that I've seen before include "Slowly change" , "Reveal a secret" , "Grow slowly" , "Develop gradually over a long time" , "Cartoon sailor" .)

I've seen this clue in The Times.

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