Guess me : On six feet, I am a noxious drink, Of whose effects you shudder to think. Change only my second foot.........

Question

On six feet, I am a noxious drink,
Of whose effects you shudder to think.
Change only my second foot, and then
You convert me into a horrible den
Where the culprit, who gave the noxious drink,
Awaits the fate of which you shudder to think.
What am i ?

Answer 1

Poison or Prison

"On six feet"

means a six letter word. The first two lines refer to poison. The next two lines refer to prison. The last two refers to where

"the culprit"

who gave you the poison would go to prison.

Answer 2

Poison .....