Long drink contains very soft fruit (9)
I believe the answer is:
pineapple
'fruit' is the definition.
(pineapple is a kind of fruit)
'long drink contains very soft' is the wordplay.
'long' becomes 'pine' ('pine' can be a synonym of 'long'**).
'drink' becomes 'ale' (ale is a kind of drink).
'contains' indicates putting letters inside.
'very soft' becomes 'pp'.
'ale' placed around 'pp' is 'apple'.
'pine'+'apple'='PINEAPPLE'
(Other definitions for pineapple that I've seen before include "that might go off?" , "Juicy tropical fruit or slang hand grenade" , "Large fleshy fruit with a tuft of stiff leaves" , "Juicy tropical fruit often sold segmented" , "One may go off" .)