Bloodsucker to make escape we hear (4)
I believe the answer is:
flea
'bloodsucker' is the definition.
(I've seen this before)
'escape we hear' is the wordplay.
'escape' becomes 'flee' (I've seen this before).
'we hear' indicates a 'sounds like' (homophone) clue.
'flee' is a homophone of 'FLEA'.
'to make' acts as a link.
(Other definitions for flea that I've seen before include "Bug" , "little pest" , "Leaping insect" , "In your ear, this insect is a rebuke" , "Wingless, jumping insect" .)