Quibbling sabotaged pious act (8)
I believe the answer is:
captious
'quibbling' is the definition.
(thesaurus)
'sabotaged pious act' is the wordplay.
'sabotaged' is an anagram indicator.
'pious'+'act'='piousact'
'piousact' with letters rearranged gives 'CAPTIOUS'.
(Other definitions for captious that I've seen before include "Inclined to find fault" , "Fault-finding" , "Tending to find fault" , "Carping" , "Raising petty objections" .)