The most common and most likely answer to this crossword clue is the 9 letter word BLACKJACK
I've seen this crossword clue in The Times
B
L
A
C
K
J
A
C
K
More clues leading to the result BLACKJACK
- Flag by the end of gloomy game
- Refuse to deal with sailor showing pirate's flag
- Need Juliet in support for game
- Want Judge to come in to support club
- Old Queen has time to try and ban sailor’s game
- Quite high-ranking club, say, one might play in this game
- 21 Club
- A pictorial club maybe for a game of cards
- Need bit of joist in support for flag
Buddy explains!

The straight part
We know that "pirate's flag" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case pirate's flag = blackjack.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 BLACKJACK mean?
BLACKJACK noun- A common gambling card game in casinos, where the object is to get as close to 21 without going over.
- A hand in the game of blackjack consisting of a face card and an ace.
- The flag (i.e., a jack) traditionally flown by pirate ships; popularly thought to be a white skull and crossed bones on a black field (the Jolly Roger).
- A small, flat, blunt, usually leather-covered weapon loaded with heavy material such as lead or ball bearings, intended to inflict a blow to the head that renders the victim unconscious with diminished risk of lasting cranial trauma.
- Any of several species of weed of genus Bidens, such as Bidens pilosa, in the family Compositae.
- A blackjack oak.
- To strike with a blackjack or similar weapon.