Quiet and enthusiastic about religion (6)

I believe the answer is:

shinto

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'religion' is the definition.
(I know that Shinto is a type of religion)

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for shinto that I've seen before include "Japanese cult" , "State religion of Japan until 1945" , "Japanese religion revering ancestors" , "Religious system" , "Japanese worship" .)

I've seen this clue in The Telegraph, The Times, The Sunday Times and The Sun.

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