Leading European twice acquiring posh rug (6)
I believe the answer is:
toupee
'rug' is the definition.
(rug can informally mean a wig or toupee)
'leading european twice acquiring posh' is the wordplay.
'leading' becomes 'top' (both can mean first-class).
'european' becomes 'E' (abbreviation e.g. EU).
'twice' says to double the letters.
'acquiring' indicates putting letters inside.
'posh' becomes 'u' (abbreviation for upper-class - opposite to non-u).
'e' duplicated is 'ee'.
'top'+'ee'='topee'
'topee' going around 'u' is 'TOUPEE'.
(Other definitions for toupee that I've seen before include "False hairpiece" , "21 Antrim promontory" , "Wig or hairpiece in America" , "Hair piece" , "Small wig" .)