A fetching thing for a sporting dog to do (8)

I believe the answer is:

retrieve

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'do' is the definition.
Although both the answer and definition are verbs in their base form, I cannot see how they can define each other.

I can't explain the remainder of the clue.

Can you help me to learn more?

(Other definitions for retrieve that I've seen before include "Win back" , "Find and bring back" , "Search for and discover" , "Regain or fetch" , "Recover" .)

I've seen this clue in the Evening Standard.

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