The most common and most likely answer to this crossword clue is the 5 letter word DEIST
D
E
I
S
T
More clues leading to the result DEIST
- One believes tide's turned
- Believer bound for rejection hugs son
- Non-religious believer is grabbed by antisocial youth from behind
- Stop: one son’s missing, I believe
- Believer — in the lower social classes?
- Prude is taunted – sort of believer to hide away here
- Healer ignoring religious text remains believer in God
- Medical practitioner feared by many discards books, being a believer
- Stop rejecting the heart of Jesus to become a believer
Buddy explains!

The straight part
We know that "believer (" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case believer ( = deist.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.