Is this correct French- tu joues un sport?

"Tu fais du sport", using the verb "faire", to do, is standard in French. Common questions are "est-ce que tu fais du sport" (do you play (any) sport), "qu'est-ce que tu fais comme sport ?" (what sport do you play /practice).

But you can use the verb "jouer" in such phrases as "je joue au basket" (I'm playing Basketball), "J'aime jouer au foot" (I like to play football).