Treacherous, unlike Jacob (5)
I believe the answer is:
hairy
This clue is a double definition.
'treacherous' is the first definition.
(thesaurus)
'unlike jacob' is the second definition.
(biblical Jacob is hairless unlike his brother Esau)
(Other definitions for hairy that I've seen before include "Having had a close shave? Not so" , "Having shock" , "Armpits can be" , "Frightening - like a bear?" , "description of Jacob's brother Esau" .)