Not everyone follows Number One being offensive (7)
I believe the answer is:
noisome
'being offensive' is the definition.
(similar in meaning)
'not everyone follows number one' is the wordplay.
'not everyone' becomes 'some' (I've seen this in another clue).
'follows' means one lot of letters go next to another.
'number one' becomes 'no i' (resembles No 1).
'some' after 'noi' is 'NOISOME'.
(Other definitions for noisome that I've seen before include "Nasty" , "Foul-smelling, noxious" , "Repellent" , "Rank" , "Disagreeable, unpleasant" .)