Aggravated by lie altered on purpose (12)
I believe the answer is:
deliberately
'on purpose' is the definition.
('deliberately' can be a synonym of 'on purpose')
'aggravated by lie altered' is the wordplay.
'aggravated' indicates an anagram.
'by'+'lie'+'altered'='byliealtered'
'byliealtered' anagrammed gives 'DELIBERATELY'.
(Other definitions for deliberately that I've seen before include "On purpose" , "Consciously and intentionally" , "as intended" .)