Prince wearing drunkard's hat (6)
I believe the answer is:
topper
'hat' is the definition.
(I know that topper is a type of hat)
'prince wearing drunkard's' is the wordplay.
'prince' becomes 'p' (abbreviation).
'wearing' indicates putting letters inside.
'drunkard' becomes 'toper' (I've seen this before).
'p' inserted into 'toper' is 'TOPPER'.
(Other definitions for topper that I've seen before include "Hat for formal occasions" , "Top hat (colloq.)" , "Type of hat (informal)" , "expensive hat" , "Informally a tall hat - the best" .)