Emblem of danger (3,4)
I believe the answer is:
red flag
'emblem of danger' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for red flag that I've seen before include "Socialist symbol" , "Warning signal" , "Danger warning" , "Revolutionary symbol and song to the tune of Tannenbaum" , "Emblem of socialist revolution or danger" .)