Lab coat problem? (4)
I believe the answer is:
flea
'lab coat problem?' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for flea that I've seen before include "Biting type" , "In one's ear, it's a stinging rebuke" , "Wingless, jumping insect" , "In your ear, this insect is a rebuke" , "Blood-sucking parasites" .)