Contemplate change in friend (8)
I believe the answer is:
meditate
'contemplate' is the definition.
(I know that contemplate can be written as meditate)
'change in friend' is the wordplay.
'change' becomes 'edit' (edit can mean to change or alter).
'in' indicates putting letters inside.
'friend' becomes 'mate' (mate is a kind of friend).
'edit' put into 'mate' is 'MEDITATE'.
(Other definitions for meditate that I've seen before include "Spend time in thought" , "Cogitate" , "Think intently and at length" , "Think contemplatively" , "Ponder" .)