Contemplate friend consuming awful diet (8)
I believe the answer is:
meditate
'contemplate' is the definition.
('meditate' can be a synonym of 'contemplate')
'friend consuming awful diet' is the wordplay.
'friend' becomes 'mate' (mate is a kind of friend**).
'consuming' is an insertion indicator.
'awful' indicates an anagram.
'diet' with letters rearranged gives 'edit'.
'mate' placed around 'edit' is 'MEDITATE'.
(Other definitions for meditate that I've seen before include "Spend time in thought" , "Think to relax one's mind" , "Ruminate" , "Engage in contemplation" , "Think deeply and quietly" .)