Crackers - or what they're required for? (4)
I believe the answer is:
nuts
'crackers' is the definition.
(synonyms)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for nuts that I've seen before include "Delivers 24 [HEADBUTT]" , "Metal fasteners" , "Fruits; insane" , "Barmy (colloq)" , "Nibbles" .)