Unpleasantly vivid (5)
I believe the answer is:
lurid
'unpleasantly vivid' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for lurid that I've seen before include "Bright and garish" , "Glaringly bright" , "Gloomily threatening" , "In shocking detail" , "Ghastly in appearance" .)