Disagreement disregarding Republican lie (7)
I believe the answer is:
fiction
'lie' is the definition.
(I've seen this before)
'disagreement disregarding republican' is the wordplay.
'disagreement' becomes 'friction' (I've seen this before).
'disregarding' is a deletion indicator.
'republican' becomes 'R' (political abbreviation).
'friction' with 'r' taken out is 'FICTION'.
(Other definitions for fiction that I've seen before include "Something invented" , "Invented story" , "Novel writing" , "Imaginary prose" , "Literary genre" .)