The King altered lives (5)
I believe the answer is:
elvis
'the king' is the definition.
(I've seen this in another clue)
'altered lives' is the wordplay.
'altered' is an anagram indicator.
'lives' anagrammed gives 'ELVIS'.
(Other definitions for elvis that I've seen before include "The familiar R 'n'Roll king" , "Mr Presley" , "US singer; lives (anag.)" , "'The King' (singer)" , "The King, d. 1977" .)