Head away from carnival? Just the opposite (6)
I believe the answer is:
unfair
'just the opposite' is the definition.
(unfair is the opposite of just)
'head away from carnival?' is the wordplay.
'head away from' means to remove the first letter (I've seen 'heading away from' mean this).
'carnival?' becomes 'funfair'.
'funfair' with its initial letter taken off is 'UNFAIR'.
(Other definitions for unfair that I've seen before include "Foolishness" , "Swizz!" , "Affected by partiality - dishonest" , "Not cricket?" , "Not equitable or even-handed" .)