Almost wake up to trailblazer (5)
I believe the answer is:
comet
'trailblazer' is the definition.
(object which blazes a trail across the sky)
'almost wake up' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'wake up' becomes 'cometo' (I've seen this before).
'cometo' with its last letter removed is 'COMET'.
'to' is the link.
(Other definitions for comet that I've seen before include "High-flyer" , "Orbiting extraterrestrial body" , "Heavenly body with a fiery tail" , "Small extraterrestrial body" , "Plane" .)