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' says to take the initial letters.
'in' means one lot of letters goes inside another.
'beer' becomes 'ale' (type of beer).
The initial letters of 'perhaps preserved' is 'pp'.
'pp' going within '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" .)