The most common and most likely answer to this crossword clue is the 3 letter word LOO
L
O
O
More clues leading to the result LOO
Buddy explains!

The straight part
We know that "card game" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case card game = loo.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 LOO mean?
LOO verb- (used with at, upon or infinitive) To urge on with cries of loo or by other shouting or outcry.
- A cry to urge on hunting dogs.
- A meaningless chant or refrain.
- A trick-taking card game popular in 17th-century England, where each player is dealt three or five cards.
- The penalty paid to the pool in lanterloo for breaking certain rules or failing to take a trick.
- An act that prompts such a penalty.
- A game of lanterloo.
- Any group of people.
- To beat in the card game lanterloo.
- To pay a penalty to the pool for breaking certain rules or failing to take a trick in lanterloo.
- To pay any penalty to any community.
- A half-mask, particularly those velvet half-masks fashionable in the 17th century as a means of protecting women's complexion from the sun.
- A hot dust-bearing wind found in Bihar, Uttar Pradesh and the Punjab.
- A lavatory: a room used for urination and defecation.
- A toilet: a fixture used for urination and defecation.
- Lieutenant.