Answer: HISS

AnswerCrossword Clue
HISSBoo follower
HISSExpress displeasure
HISSSibilant boo
HISSBlow off steam
HISSSign of a leak
HISSCatcall
HISSSign of an escape?
HISSHardly a sign of support
HISSMake like a snake
HISSBoo's partner
HISSSerpent's greeting
HISSDisapproving sound
HISSSerpent's sound
HISSLeak indicator
HISSBlow off steam?
HISSSlow leak sound
HISSLet off steam
HISSGive the villain his due
HISSSound from an arch-backed cat
HISSUnhappy fan's reaction
hisshissing sound
HISSSnake speech
HISSGreet the villain
HISSCat's warning
HISSSound of air escaping
HISSAlber ..
HISSCatty warning
HISS"Back off!" in felinese?
HISSGreet a villain
HISSSibilant threat
HISSViper's "Back off!"
HISSSound of disapproval
HISSStage villain's voice
HISSBoo relative
HISSA villain might draw one
HISSSerpent's warning
HISSSnake's sound
HISSHeckle sibilantly
HISSRadiator sound
HISSSound of escaping air