Guide dog (7)

I believe the answer is:

pointer

I believe this clue is a double definition.

'guide' is the first definition.
(I've seen this before)

'dog?' is the second definition.
(pointer is a kind of dog)

(Other definitions for pointer that I've seen before include "Arrow" , "Smooth-haired game-dog" , "Hint (for a dog?)" , "Sign" , "something moved by mouse" .)

I've seen this clue in The Independent, The Guardian and The Telegraph.

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