The most common and most likely answer to this crossword clue is the 7 letter word EXPUNGE
I've seen this crossword clue in The Guardian
E
X
P
U
N
G
E
More clues leading to the result EXPUNGE
- Get rid of old joke, becoming trite ultimately
- Get rid of old joke, perhaps, for a comeback?
- Former wordplay, originally good enough for 3
- Get rid of old lover with little witticism and say that’s over
- Remove old joke, anticipating grand finale of Fringe
- Get rid of old dog without new drug
- Eliminate veiled content in sex pun, generally
- Raze old building finally in Indian city
- Delete old joke generalizing ethnicities, basically
- Erase old joke finally giving offence
Buddy explains!

The straight part
We know that "Get rid of" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case get rid of = expunge.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does EXPUNGE mean?
EXPUNGE verb- To erase or strike out.
- To eliminate completely; annihilate.
- To delete permanently (e-mail etc.) that was previously marked for deletion but still stored.