A study occupied by posh poet (5)
I believe the answer is:
auden
'poet' is the definition.
(Auden is an example)
'a study occupied by posh' is the wordplay.
'study' becomes 'den' (term for a study or office).
'occupied by' means one lot of letters goes inside another.
'posh' becomes 'u' (abbreviation for upper-class - opposite to non-U).
'a'+'den'='aden'
'aden' placed around 'u' is 'AUDEN'.
(Other definitions for auden that I've seen before include "20th-century Anglo-American poet" , "US poet born in Britain" , "British-born American poet" , "W. H. ... (British poet)" , "Poet, associate of Spender and Isherwood" .)