Menacing coming from the left (8)
I believe the answer is:
sinister
I believe this clue is a double definition.
'menacing' is the first definition.
('sinister' can be a synonym of 'menacing')
'the left' is the second definition.
(thesaurus)
'coming from' is the link.
(Other definitions for sinister that I've seen before include "Suggestive of evil, being lefthanded" , "Threatening - ominous" , "Threatening the left in heraldry" , ", nun going round home" , "Disquieting" .)