Betrayed crook pocketing child's last toy (5,4)
I believe the answer is:
teddy bear
'toy' is the definition.
(teddy bear is a type of toy)
'betrayed crook pocketing child's last' is the wordplay.
'crook' indicates an anagram (a crooked or broken form of the letters).
'pocketing' is an insertion indicator (pocket can mean to steal or take possession of).
'last' says to take the final letters.
The last letter of 'child' is 'd'.
'betrayed' with letters rearranged gives 'tedybear'.
'tedybear' going around 'd' is 'TEDDY BEAR'.
(Other definitions for teddy bear that I've seen before include "Popular cuddly toy" , "what kid may be allowed at bedtime" , "cling to this for comfort?" , "Soft toy" , "Stuffed toy" .)