Unparalleled money gained penning short story (12)
I believe the answer is:
incomparable
'unparalleled' is the definition.
(similar in meaning)
'money gained penning short story' is the wordplay.
'money gained' becomes 'income' (I've seen this before).
'penning' means one lot of letters goes inside another.
'short' means to remove the last letter.
'story' becomes 'parable' (parable is a kind of story).
'parable' with its last letter taken off is 'parabl'.
'income' enclosing 'parabl' is 'INCOMPARABLE'.
(Other definitions for incomparable that I've seen before include "Unequalled" , "Unrivalled" , "like no one else?" , "Matchless" , "Second-to-none" .)