Be highly noticeable (5,3)
I believe the answer is:
stand out
'be highly noticeable' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for stand out that I've seen before include "Be conspicuous, or persist in demands" , "Be prominent or superior" , "Distinguish oneself" , "Refuse to agree - project" , "Be conspicuous, or persist in demand" .)