Wiped out by joke penned by eg top journo (8)
I believe the answer is:
expunged
'wiped out' is the definition.
(I've seen this in another clue)
'by joke penned by eg top journo' is the wordplay.
'by' becomes 'x' (2 by 4 is 2 x 4).
'joke' becomes 'pun' (pun is a type of joke).
'penned by' means one lot of letters goes inside another (inserted letters are penned in).
'top journo' becomes 'ed' (editor, leading journalist).
'x'+'pun'='xpun'
'xpun' placed inside 'eg' is 'expung'.
'expung'+'ed'='EXPUNGED'
(Other definitions for expunged that I've seen before include "Excised, struck out" , "Excised, scratched out" , "Erased" , "Wiped or rubbed out" .)