Changed the heart of every cop at the end of Earth Day (6)
I believe the answer is:
edited
'changed' is the definition.
(editing is a kind of changing)
'the heart of every cop at the end of earth day' is the wordplay.
'the heart of' says to take the centre.
'cop' becomes 'DI' (detective inspector).
'the end of' says to take the final letters.
'earth' becomes 'E'.
'day' becomes 'd' (abbreviation for day).
The centre of 'every' is 'e'.
The final letter of 'at' is 't'.
'e'+'di'+'t'+'e'+'d'='EDITED'
(Other definitions for edited that I've seen before include "Prepared a paper" , "Amended" , "Prepared text for publication" , "Changed for going out" , "Prepared printed material for publication" .)