A stuck-up politician, rude (10)
I believe the answer is:
Here is my best explanation:
'rude' is the definition.
'a stuck-up politician' is the wordplay.
'stuck' becomes 'gored'.
'up' is a reversal indicator (in down clue: letters go upwards).
'politician' becomes 'tory' (I've seen this before).
'agored' back-to-front is 'deroga'.
(Other definitions for derogatory that I've seen before include "Disparaging", "deliberately offensive", "Showing a disrespectful attitude", "Disrespectful", "Insulting", "insulting" and "Offensive".)