Cutting into beef, angular tooth (4)
I believe the answer is:
'tooth' is the definition.
(fang is a kind of tooth)
'cutting into beef angular' is the wordplay.
'cutting into' says the answer is hidden in the clue.
'FANG' is hidden within 'beef angular'.
(Other definitions for fang that I've seen before include "Venomous tooth", "Dracula's tooth?", "nipper", "Large canine tooth", "Large pointed tooth".)