The most common and most likely answer to this crossword clue is the 9 letter word STRATAGEM
I've seen this crossword clue in The Times
S
T
R
A
T
A
G
E
M
More clues leading to the result STRATAGEM
- Learned motorway is masking restaurant plot
- Magistrate perversely rejecting current plan
- Plan to sabotage regattas on first of May
- Plan to get great pies brought round
- Flipping hookers wrecked game plan
- Manoeuvre to find precious stone under geological layers
- Plan to reject extremely good pastry dishes
- Trick turning over gigantic pastries?
- Plan to have upside-down cakes on a rock!
- Huge quiches coming up — that’s the plan
Buddy explains!

The straight part
We know that "plan" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case plan = stratagem.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 STRATAGEM mean?
STRATAGEM noun- A tactic or artifice designed to gain the upper hand, especially one involving underhanded dealings or deception.