Outrage seeing altar boy oddly on town (8)
I believe the answer is:
atrocity
'outrage' is the definition.
(thesaurus)
'altar boy oddly on town' is the wordplay.
'oddly' means one should take alternating letters.
'on' means one lot of letters go next to another.
'town' becomes 'city' (I've seen this in other clues**).
'altar'+'boy'='altarboy'
The alternate letters of 'altarboy' are 'atro'.
'atro'+'city'='ATROCITY'
'seeing' is the link.
(Other definitions for atrocity that I've seen before include "Barbarity, inhumanity" , "Wickedness" , "Appalling act" , "Cruel deed" , "villainy" .)