Fruit perhaps preserved primarily in beer (5)
I believe the answer is:
apple
'fruit' is the definition.
(apple is a kind of fruit)
'perhaps preserved primarily in beer' is the wordplay.
'primarily' indicates taking the first letters.
'in' means one lot of letters goes inside another.
'beer' becomes 'ale' (type of beer).
The first letters of 'perhaps preserved' is 'pp'.
'pp' inserted inside 'ale' is 'APPLE'.
(Other definitions for apple that I've seen before include "Firm round fruit" , "Jonathan, for example" , "One poisoned Disney's Snow White" , "Eve's fruit" , "New York the Big one" .)