Sought to justify former copper's heartless intent (7)
I believe the answer is:
excused
'sought to justify' is the definition.
(to excuse something is to try to justify it)
'former copper's heartless intent' is the wordplay.
'former' becomes 'ex' (prefix meaning former or onetime).
'copper's' becomes 'Cu's' (chemical symbol).
'heartless' says to hollow out the word (remove centre letters).
'intent' becomes 'end' (I've seen this in other clues).
'end' with its centre removed is 'ed'.
'ex'+'cus'+'ed'='EXCUSED'
(Other definitions for excused that I've seen before include "Given permission to leave, or pardoned" , "Granted exemption" , "Made allowances for" , "Let off (a duty)" , "Exonerated" .)