Stupid to put toddlers on this? (5)
I believe the answer is:
potty
I believe this is a double definition.
'stupid' is the first definition.
(both can mean foolish or mad)
'put toddlers on this?' is the second definition.
(a potty is used to toilet-train a toddler)
'to' is the link.
(Other definitions for potty that I've seen before include "Nuts" , "Bonkers" , "Daft (informal)" , "Infant's loo" , "Mad" .)