1/ I disapprove;
2/ You've been naughty;
3/ What a shame;
4/ How embarrassing for you;
5/ Isn't life unfair sometimes!
6/ I commiserate with your sadness/suffering/ill treatment.
Sometimes represented as Tch Tch or Tut Tut, Tsk is more a vocal sound than an actual word, and "pronounced" by forming a T-sound, but then sucking lightly on the palate. People only say "Tisk tisk" as a parody of the actual sound, making fun of the act of disapproval or shaming.
1/ Tsk Tsk! You're far too young to smoke!
2/ Tsk tsk, Tracking mud inside? I'm telling on you!
3/ Homeless and derelict, at age 20? Tsk tsk!
4/ They called you that in front of everybody? Tsk tsk!
5/ All those people, thrown out of work for the sake of more profits? Tsk tsk!
6/ You poor thing, three broken bones in one year? Tsk tsk!
"Work it" usually means, "strut your stuff," show off your assets, make some physical attribute (figure, walk, style of dress, etc.) to "work" for you to make you attractive.
While not proven or confirmed, the expression may have originated among "working girls," i.e. prostitutes/street walkers, who would make a sultry walk etc. "work" for them to attract business. If it did have that connotation, it has been lost with time, and now usually is applied more innocently.
Damn, you looking hot! Work it, girl!