Biscuits or nuts (8)
I believe the answer is:
crackers
This clue is a double definition.
'biscuits' is the first definition.
(I've seen this before)
'nuts' is the second definition.
(both can informally mean mad)
'or' is the link.
(Other definitions for crackers that I've seen before include "Crazy types" , "Mad - biscuits" , "Mad - fireworks" , "Yanks open these" , "Insane" .)