The most common and most likely answer to this crossword clue is the 3 plus 5 letter word OLD HARRY
I've seen this crossword clue in The Times
O
L
D
H
A
R
R
Y
More clues leading to the result OLD HARRY
Buddy explains!

The straight part
We know that "Who's the host from Hell" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case who's the host from hell = old harry.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.