Bloodsucking fly (6)
I believe the answer is:
tsetse
'bloodsucking fly' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for tsetse that I've seen before include "cause of sleepiness?" , "African transmitter" , "carrier of disease" , "source of sleeping sickness" , "Bloodsucking African fly" .)