Fool that may get in your hair (3)
I believe the answer is:
nit
I believe this clue is a double definition.
'fool' is the first definition.
(both can mean a stupid person)
'that may get in your hair' is the second definition.
(insect egg in one's hair)
(Other definitions for nit that I've seen before include "Eg of louse" , "Stupid person; egg" , "Parasite's egg made of tin" , "Louse's egg; idiot" , "Egg of parasitic insect" .)