The most common and most likely answer to this crossword clue is the 8 letter word EXORCIST
I've seen this crossword clue in Independent
E
X
O
R
C
I
S
T
More clues leading to the result EXORCIST
- He hopes to relieve people of their unwanted possessions
- One sent to relieve another of possessions?
- One releasing those caught in possession?
- Be harbouring monster? Here’s one to help!
- Crucifix finally found during cries to arrange for a priest with special powers …
- One banishes spirits from former soldiers sitting on tomb
- Expert wished good riddance?
- Who will make you live without imaginary demon?
- Person downing the spirits?
- One used to lift one’s spirits?
Buddy explains!

The straight part
We know that "Here’s one to help" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case here’s one to help = exorcist.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.
What does EXORCIST mean?
EXORCIST noun- A person, especially a priest, who practices exorcism.