Posh bird mentioned African country (6)
I believe the answer is:
uganda
'african country' is the definition.
(country in Africa)
'posh bird mentioned' is the wordplay.
'posh' becomes 'u' (abbreviation for upper-class - opposite to non-U).
'bird' becomes 'gander' (male goose).
'mentioned' shows a homophone (sound like).
'gander' sounds like 'ganda'.
'u'+'ganda'='UGANDA'
(Other definitions for uganda that I've seen before include "It was Idi Amin's country" , "literally the centre for sugar?" , "African country once ruled by Idi Amin, capital Kampala" , "Idi Amin used to rule this African state" , "Country W. of Kenya" .)