Convert fancy housing for dog, in retirement (6)

I believe the answer is:

modify

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'convert' is the definition.
(I know that convert is a kind of modify)

I can't explain the rest of the clue.

(Other definitions for modify that I've seen before include "Adapt" , "Alter slightly" , "Make partial changes to" , "Revise" , "Adjust" .)

I've seen this clue in The Telegraph.

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