Nothing is fruit (6)
I believe the answer is:
olives
'nothing is fruit' is the definition.
I can't tell whether this defines the answer.
'nothing is' is the wordplay.
'nothing' becomes 'O' (looks like zero - 0).
'is' becomes 'lives'.
'o'+'lives'='OLIVES'
Can you help me to learn more?
(Other definitions for olives that I've seen before include "Small green Mediterranean tree fruits" , "The fruits are important source of oil" , "Small tree-fruits - so live" , "Trees grown for their oil-producing fruit" , "Small green stone fruits, nice in cocktails" .)