Genuine scare, heading off (5)
I believe the answer is:
right
'genuine' is the definition.
(both can mean proper)
'scare heading off' is the wordplay.
'scare' becomes 'fright' (synonyms).
'heading off' means to remove the first letter.
'fright' with its first letter taken away is 'RIGHT'.
(Other definitions for right that I've seen before include "The hand to the east when facing north" , "One has a claim to be correct" , "Due" , "correctly" , "Complete" .)