Change 'observe' into the opposite (7)
I believe the answer is:
obverse
'the opposite' is the definition.
(I've seen this before)
'change observe' is the wordplay.
'change' indicates anagramming the letters.
'observe' with letters rearranged gives 'OBVERSE'.
'into' is the link.
(Other definitions for obverse that I've seen before include "Side of a coin bearing the head" , "Side of coin that bears head or principle design" , "monarch's head here" , "Side of a coin that shows heads" , "Verbose about coin side" .)