Religious man is distant hiding heart of purist (5)
I believe the answer is:
friar
'religious man' is the definition.
(I've seen this before)
'distant hiding heart of purist' is the wordplay.
'distant' becomes 'far' (synonyms).
'hiding' is an insertion indicator.
'heart of' says to take the centre.
The middle letters of 'purist' are 'ri'.
'far' placed around 'ri' is 'FRIAR'.
'is' acts as a link.
(Other definitions for friar that I've seen before include "Member of one of the four mendicant orders" , "Eg, a Dominican" , "he offers religious teaching?" , "Mendicant monk" , "Male member of a mendicant religious order" .)