STIFFEN is a playable word

stiffen Scrabble® Dictionary

verb
stiffened, stiffening, stiffens
to make stiff
92 Playable Words can be made from "STIFFEN"
   2-Letter Words (13 found)
   3-Letter Words (27 found)
   6-Letter Words (3 found)
   7-Letter Words (1 found)