The most common and most likely answer to this crossword clue is the 5 plus 8 letter word SMEAR CAMPAIGN
S
M
E
A
R
C
A
M
P
A
I
G
N
More clues leading to the result SMEAR CAMPAIGN
- Attempt to discredit press cameraman — pigs!
- Magic Parmesan recipe for political skulduggery
- A screaming loony grabs a politician in attempt to bring discredit
- Crooked P R maniac’s game a slanderous plan to discredit
- Manager is upset about side making attacks on reputation?
- Reams rewritten by activist unhesitantly in attempt to defame
- Proof includes camera rolls featuring a politician’s plan to discredit
- Notice crowd in some odd area having a gin cocktail and mudslinging
- German maps CIA produced for false propaganda
- “Pigs” — Cameraman’s botched plan to disgrace someone
Buddy explains!

The straight part
We know that "plan to discredit" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case plan to discredit = smear campaign.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.