Country a front for undesirables (4)

I believe the answer is:

peru

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'country' is the definition.
(I know that Peru is South American country)

'a front for undesirables' is the wordplay.
'a' becomes 'per' (eg 'one a day' means 'one per day').
'front for undesirables' becomes 'u' (I am not sure about this - if you are sure you should believe this answer much more).
'per'+'u'='PERU'

Can you help me to learn more?

(Other definitions for peru that I've seen before include "S American country, capital Lima" , "Mario Vargas Llosa's country" , "Country of Lima, Cuzco and Paddington Bear" , "Paddington Bear's country of birth" , "Land of the Incas" .)

I've seen this clue in the Sydney Morning Herald.

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