Alter, modify (6)
I believe the answer is:
change
This clue is a double definition.
'alter' is the first definition.
(I know that alter is a kind of alter)
'modify' is the second definition.
(I know that modify is a kind of change)
(Other definitions for change that I've seen before include "Transfer" , "reform" , "Make different; coins" , "Innovation" , "Coins of low value" .)