Nonconformist priest nearby indisposed (12)
I believe the answer is:
presbyterian
'nonconformist' is the definition.
'priest nearby indisposed' is the wordplay.
'indisposed' indicates anagramming the letters.
'priest'+'nearby'='priestnearby'
'priestnearby' with letters rearranged gives 'PRESBYTERIAN'.
(Other definitions for presbyterian that I've seen before include "Minister, perhaps" , "Sort of Christian - priest nearby (anag)" , "Type of Christian -- best in prayer (anag)" , "church member" , "Form of church deriving from Calvin and Knox" .)