Repeated greeting for a toy (4)
I believe the answer is:
yoyo
'for a toy' is the definition.
(I've seen this before)
'repeated greeting' is the wordplay.
'repeated' shows that letters should be duplicated.
'greeting' becomes 'yo'.
'yo' doubled is 'YOYO'.
(Other definitions for yoyo that I've seen before include "Item on string" , "Toy" , "Plaything" .)