Biter bit after losing protection of son (5)
I believe the answer is:
midge
'biter' is the definition.
I don't understand how the remainder of the clue works.
(Other definitions for midge that I've seen before include "A small biting gnat-like insect" , "Be an obstacle" , "Two-winged fly" , "Tiny swarming insect" , "Small flying insect" .)