Evidence cake's been swiped? Good Lord! (6)
I believe the answer is:
crumbs
If this is the answer I cannot explain how the clue works.
Can you help me to learn more?
(Other definitions for crumbs that I've seen before include "Schoolboy expression (of comfort?)" , "Tiny pieces of bread or cake" , "Very little to eat -- goodness gracious me!" , "not much of a bloomer!" , "Little things offering minimal comfort" .)