Bonehead embraced by mother _ the snake! (5)
I believe the answer is:
mamba
'snake' is the definition.
(mamba is a kind of snake)
'bonehead embraced by mother' is the wordplay.
'bonehead' becomes 'b' (head letter of 'bone').
'embraced by' is an insertion indicator.
'mother' becomes 'mama' (mama informally means mother).
'b' inserted within 'mama' is 'MAMBA'.
'the' acts as a link.
(Other definitions for mamba that I've seen before include "serpent" , "Snake that might kill" , "venomous crawler" , "Deadly creature" , "Death-dealing African" .)