I ate crab riddled with parasites (8)
I believe the answer is:
bacteria
'with parasites' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'i ate crab riddled' is the wordplay.
'i ate crab' can be anagrammed to 'BACTERIA'.
Though, I am unsure how this is indicated.
Can you help me to learn more?
(Other definitions for bacteria that I've seen before include "Microscopic organisms, good and bad" , "Single cell micro-organisms" , "Microscopic organisms, may carry diseases" , "Tiny organisms, may be good or bad" , "Infectious organisms" .)