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