Rodent found in African country by gannet (6,3)

I believe the answer is:

guinea pig

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'rodent' is the definition.
(guinea pig is a kind of rodent)

'african country by gannet' is the wordplay.
'african country' becomes 'Guinea' (country in Africa).
'by gannet' becomes 'pig' (I can't explain this - if you can you should believe this answer much more).
'guinea'+'pig'='GUINEA-PIG'

'found in' is the link.

Can you help me to learn more?

(Other definitions for guinea pig that I've seen before include "Volunteer" , "rodent eaten in Peru" , "Subject of trial" , "Pet - subject of experiment" , "South American cavy" .)

I've seen this clue in The Times.

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