Unlimited number misidentifying missing midges (8)
I believe the answer is:
infinity
'unlimited number' is the definition.
'infinity' can be an answer for 'number' (thesaurus). I am not sure about the 'unlimited' bit.
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for infinity that I've seen before include "Time or space without limit" , "Endlessness or boundlessness" , "A number larger than any finite value, mathematically" , "There's no end to" , "A very great number" .)