Work place around Post Office counter (8)
I believe the answer is:
opposite
'counter' is the definition.
(thesaurus)
'work place around post office' is the wordplay.
'work' becomes 'op' (abbreviation for opus).
'place' becomes 'site' ('site' can be a synonym of 'place'**).
'around' means one lot of letters goes inside another.
'post office' becomes 'po'.
'op'+'site'='opsite'
'opsite' enclosing 'po' is 'OPPOSITE'.
(Other definitions for opposite that I've seen before include "Reverse or antithesis" , "Diametrically contrary" , "Totally different; facing" , "Contrary, antithetical" , "Corresponding" .)