The most common and most likely answer to this crossword clue is the 8 letter word DITHEISM
I've seen this crossword clue in Financial Times
D
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More clues leading to the result DITHEISM
Buddy explains!
The straight part
We know that "believing in two gods" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case believing in two gods = ditheism.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 DITHEISM mean?
DITHEISM noun- A belief in two deities, which may be in conflict with each other.