SLACK is a playable word

slack Scrabble® Dictionary

adjective
slacker, slackest
not tight or taut
verb
slacked, slacking, slacks
to slacken
21 Playable Words can be made from "SLACK"
   2-Letter Words (4 found)
   3-Letter Words (9 found)
   4-Letter Words (5 found)
   5-Letter Words (3 found)