Bore's terrible tirade about compiler (8)
I believe the answer is:
diameter
'bore's' is the definition.
(thesaurus)
'terrible tirade about compiler' is the wordplay.
'terrible' indicates anagramming the letters.
'about' indicates putting letters inside.
'compiler' becomes 'me' (the person who is writing these clues).
'tirade' with letters rearranged gives 'diater'.
'diater' going around 'me' is 'DIAMETER'.
(Other definitions for diameter that I've seen before include "Straight line across circle passing through its centre" , "Two radii" , "width of bar" , "A demerit for line bisecting a circle" , "Width across the centre of a circle" .)