Yes, tsk is in the scrabble dictionary.

What does tsk mean?

tsk in American English

1. (a sound) used to express disapproval, genuine or mock sympathy, etc.: a click, or sucking sound, made by touching the tongue to the hard palate and rapidly withdrawing it. verb intransitiveWord forms: tsked or ˈtsking. 2. to utter this sound.

Is Tsk a word?

(used, often in quick repetition, as an exclamation of contempt, disdain, impatience, etc.) to utter the exclamation “tsk.” ...