Dry biscuit, fabulous thing (7)
I believe the answer is:
cracker
'dry biscuit' is the definition.
(I've seen this before)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for cracker that I've seen before include "often pulled at parties" , "An outstanding example of its kind!" , "Christmas table item" , "Great joke - terrible joke's container?" , "exceptional" .)