Egg container overturned (3)
I believe the answer is:
nit
'egg' is the definition.
(a nit is an insect egg)
'container overturned' is the wordplay.
'container' becomes 'tin' (tin is a kind of container).
'overturned' says the letters should be written in reverse.
'tin' written backwards gives 'NIT'.
(Other definitions for nit that I've seen before include "Young louse" , "Stupid person; egg" , "Louse's egg; idiot" , "Louse's egg - berk" , "Idiot, ass" .)