Clue: Fruit bat home? Not in, definitely out (5)
Answer: PLUMB
Explanation: Definition: definitely out
The fruit is a PLUM, then we have to read "bat home" as "b at home", and remove "at home" ("in") to be left with just the B. Hard work for single letter! The definition refers to an LBW decision in cricket where the balls hits the batsman's legs in front of the middle stump. It's from the sense of "vertical", as in a plumb line