A choice of nothing - point is obscure (6)
I believe the answer is:
option
'a choice' is the definition.
(I know that choice can be written as option)
'nothing point is obscure' is the wordplay.
'nothing' becomes 'O' (looks like zero - 0).
'is obscure' indicates anagramming the letters.
'point' with letters rearranged gives 'ption'.
'o'+'ption'='OPTION'
'of' acts as a link.
(Other definitions for option that I've seen before include "Altenative choice" , "Freedom to choose" , "Possible choice" , "Choice of portion" , "The choice of taking or leaving" .)