Uncool person (4)
I believe the answer is:
nerd
'uncool person' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for nerd that I've seen before include "Socially inept but knowledgeable person" , "One lacking social skills" , "Someone boring (about computers?)" , "Flag on poles; wide (headline)" , "Boring, trivia-obsessed type" .)