Ascribe it, perhaps, as an omen (6)
I believe the answer is:
assign
'ascribe' is the definition.
(I know that ascribe can be written as assign)
'as an omen' is the wordplay.
'an omen' becomes 'sign' (I've seen this in another clue).
'as'+'sign'='ASSIGN'
'it perhaps' acts as a link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for assign that I've seen before include "grant" , "Set aside for a specific purpose" , "Allocate, appoint" , "Apportion, ascribe" , "Nominate" .)