Child’s toy left twice after party (4)
I believe the answer is:
doll
'child's toy' is the definition.
(I've seen this before)
'left twice after party' is the wordplay.
'left' becomes 'l' (common abbreviation).
'twice' shows that letters should be duplicated.
'after' is a charade indicator (letters next to each other).
'party' becomes 'do' (do is a kind of party).
'l' doubled is 'll'.
'll' put after 'do' is 'DOLL'.
(Other definitions for doll that I've seen before include "Play figure" , "A girl's plaything" , "Toy in human form" , "Puppet" , "Toy baby" .)