Bird's preserved food? Could be a problem (3,2,5)

I believe the answer is:

can of worms

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'could be a problem' is the definition.
(a can of worms is a potentially problematic issue)

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for can of worms that I've seen before include "Potential trouble" , "Complex problem" , "this may turn out awkward" , "which shouldn't be opened" , "amateur angler's bait?" .)

I've seen this clue in The Times.

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