Insect heard to run away fast (4)
I believe the answer is:
flea
'insect' is the definition.
(I know that flea is a type of insect)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for flea that I've seen before include "Small blood-sucking insect" , "Bug" , "irritant type" , "Little jumping insect" , "Bloodsucking parasite" .)