Dons casual pants, causing outrage (10)
I believe the answer is:
scandalous
'causing outrage' is the definition.
(I've seen this before)
'dons casual pants' is the wordplay.
'pants' is an anagram indicator (UK informal term for 'nonsense' or 'rubbish').
'dons'+'casual'='donscasual'
'donscasual' is an anagram of 'SCANDALOUS'.
(Other definitions for scandalous that I've seen before include "Causing outrage" , "Highly improper" , "Shocking and offensive" , "Outrageous" , "Disgraceful" .)