Mad to offer such a stuff to the toothless (5)
I believe the answer is:
nutty
'mad' is the definition.
(I've seen this before)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for nutty that I've seen before include "Like hard fruit; mad" , "Insane" , "Mad (colloq.)" , "Like cobs, brazils, etc" , "Crazy -- tasting of almonds" .)