Crossword Genius

One's mad to have these pro­tected creatures in church (4,2,3,6)

Ross

I believe the answer is:

bats in the belfry

'one's mad to have these' is the definition.
(someone with bats in the belfry is mad)

'protected creatures in church' is the wordplay.
I cannot quite understand how this works, but
'creatures' could be 'bats' (bat is a kind of creature) and 'bats' is located in the answer.
'in' is found in the answer.
This explanation may well be incorrect...

(Another definition for bats in the belfry that I've seen is " Slightly mad".)

I've seen this clue in The Guardian.
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