Festival wind? (8)
I believe the answer is:
easterly
'festival wind?' is the definition.
'easterly' can be an answer for 'wind?' (easterly is a kind of wind). I am not certain of the 'festival' bit.
'festival wind?' is the wordplay.
'festival' becomes 'easter' (Christian festival).
'wind?' becomes 'ly' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'easter'+'ly'='EASTERLY'
Can you help me to learn more?
(Other definitions for easterly that I've seen before include "A wind blowing towards the west" , "Year's let (anag) - direction of 15" , "Of wind, blowing from direction of rising sun" , "The sort of wind that brings cold air to this country" , "Invariably cold wind" .)