Nothing's missed by card sharp (4)
I believe the answer is:
tart
'sharp' is the definition.
(I've seen this in another clue)
'nothing's missed by card' is the wordplay.
'nothing' becomes 'O' (O resembles 0).
'missed by' indicates named letters should be taken away.
'card' becomes 'tarot' (tarot cards are used to tell fortunes).
'tarot' with 'o' taken out is 'TART'.
(Other definitions for tart that I've seen before include "quiche, perhaps" , "Flan; acidic" , "Of taste, sharp or acid" , "Flat pie" , "Acidulous" .)