Tinned pickle to open? (3,2,5)
I believe the answer is:
can of worms
I'm afraid I can't even guess how this answer relates to the clue.
Can you help me to learn more?
(Other definitions for can of worms that I've seen before include "Potential trouble" , "Bird's convenience food" , "What may prove problematic" , "which shouldn't be opened" , "nasty problem" .)