Fruit is a mile off (4)
I believe the answer is:
lime
'fruit' is the definition.
(I know that lime is a type of fruit)
'mile off' is the wordplay.
'off' indicates an anagram.
'mile' is an anagram of 'LIME'.
'is a' acts as a link.
(Other definitions for lime that I've seen before include "Yellowish-green" , "Bright light green" , "Mailed item" , "Kind of tree or substance used in cement" , "Caustic calcium" .)