Drunken spree involving end of posh ball (6)
I believe the answer is:
sphere
'ball' is the definition.
(thesaurus)
'drunken spree involving end of posh' is the wordplay.
'drunken' indicates an anagram.
'involving' means one lot of letters goes inside another.
'end of' indicates one should take the final letters.
The final letter of 'posh' is 'h'.
'spree' is an anagram of 'spere'.
'spere' placed around 'h' is 'SPHERE'.
(Other definitions for sphere that I've seen before include "Particular environment or walk of life" , "Solid figure - range of activity" , "Ball, orb" , "Round solid figure with every point on its surface equidistant from its centre" , "Ball shape" .)