Line from popular campaign (3)
I believe the answer is:
arc
'line' is the definition.
(arc is a kind of line)
'from popular campaign' is the wordplay.
'from' says the answer is hidden in the clue.
'ARC' is hidden in the letters of 'popular campaign'.
(Other definitions for arc that I've seen before include "Something used to weld" , "development of plot" , "bends?" , "A curve; a discharge" , "Part of a circular line" .)