Shortening Tuesday! (4)
I believe the answer is:
suet
'shortening tuesday' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'shortening tuesday' is the wordplay.
'shortening' becomes 'sue' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'tuesday' becomes 't'.
'sue'+'t'='SUET'
Can you help me to learn more?
(Other definitions for suet that I've seen before include "Hard fat from beef and sheep" , "Solid fat used in cooking" , "Hard white cooking fat" , "Thin pancake" , "Edible fat used in cooking" .)