Chewy sweet a king fed to beast (7)
I believe the answer is:
'chewy sweet' is the definition.
(I've seen this before)
'a king fed to beast' is the wordplay.
'king' becomes 'R' (abbreviation for rex, king in Latin).
'fed to' indicates putting letters inside.
'beast' becomes 'camel' (type of animal).
'ar' put into 'camel' is 'CARAMEL'.
(Other definitions for caramel that I've seen before include "Chewy sweet - burnt sugar" , "Soft sweet" , "Soft toffee" , "Burnt sugar used for flavouring" , "Browned syrup" .)