So unless local people help us, religious leaders produce Brimstone (7)

I believe the answer is:

sulphur

'produce brimstone' is the definition.
(I know that native sulphur is a type of Sulphur)

'so unless local people help us religious leaders' is the wordplay.
'leaders' suggests taking the first letters.
The first letters of 'so unless local people help us religious' is 'SULPHUR'.

(Other definitions for sulphur that I've seen before include "Element, atomic no. 16" , "Brimstone" , "Yellow non-metallic element" , "S (chem.)" , "Chemical used in match heads" .)

I've seen this clue in the Sydney Morning Herald.

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