The most common and most likely answer to this crossword clue is the 7 letter word SCEPTIC
I've seen this crossword clue in Independent
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More clues leading to the result SCEPTIC
- I doubt decaying houses beginning to crumble
- Doubter’s stomach briefly filled with edible fungus
- Doubting Thomas infected, having caught cold
- Symbol of power not concerning one cold philosopher
- Pussy keeps heading for cream? I’m not sure
- Non-believer, small commander, holding distressed pet
- He casts doubt, festering, about origin of climate
- Way to accommodate church’s priest in charge, while remaining unconvinced
- Idea Tory dismissed sharing thus becoming a doubter
- He has doubts about entering sort of tank
Buddy explains!

The straight part
We know that "doubter" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case doubter = sceptic.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 SCEPTIC mean?
SCEPTIC noun- Someone who habitually doubts beliefs and claims presented as accepted by others, requiring strong evidence before accepting any belief or claim.
- Someone undecided as to what is true.
- A type of agnostic; someone skeptical towards religion.