Outdoor festival -- cut a cheese (4)
I believe the answer is:
feta
'cheese' is the definition.
(I've seen this before)
'outdoor festival cut a' is the wordplay.
'outdoor festival' becomes 'fete' (I've seen this before).
'cut' means to remove the last letter.
'fete' with its final letter removed is 'fet'.
'fet'+'a'='FETA'
(Other definitions for feta that I've seen before include "food there" , "Low-fat cheese" , "White and salty goat or sheep cheese" , "Greek sheep or goats' cheese" , "Type of cheese" .)