Some unusual point in portents (5)
I believe the answer is:
omens
'portents' is the definition.
('omen' can be a synonym of 'portent')
'some unusual point in' is the wordplay.
'unusual' is an anagram indicator.
'point' becomes 'n' (N is an example).
'in' indicates putting letters inside.
'some' is an anagram of 'omes'.
'omes' placed around 'n' is 'OMENS'.
(Other definitions for omens that I've seen before include "Augurs" , "Auguries" , "Signs of things to come" , "Harbingers, portents" , "Prophetic signs of good or evil" .)