Bloodsucking insect (6)
'bloodsucking insect' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for bedbug that I've seen before include "It sucks your blood while you sleep" , "Parasite between the sheets?" , "Bloodsucking insect associated with dirty houses" , "Bloodsucker's" , "Sleeper biter?" .)
(Other definitions for tsetse fly that I've seen before include "It spreads sleeping sickness" , "Cause of sleeping sickness" , "African, blood-sucking disease spreader" , "parasite" , "African insect that transmits diseases" .)