Silly boozer in New York (5)
I believe the answer is:
ninny
'silly' is the definition.
(thesaurus)
'boozer in new york' is the wordplay.
'boozer' becomes 'inn'.
'in' indicates putting letters inside.
'new york' becomes 'ny'.
'inn' going inside 'ny' is 'NINNY'.
(Other definitions for ninny that I've seen before include "dope" , "Silly billy" , "gravely so miscalled by mechanicals" , "not a wise man" , "Simpleton" .)