Traffic problem promised for tomorrow? (3)
I believe the answer is:
jam
'traffic problem' is the definition.
(I've seen this in another clue)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for jam that I've seen before include "Troublesome situation" , "Conserve" , "Fruit preserve" , "problem" , "Preserve - predicament" .)