Will have it that sins are absolved in it (6)
I believe the answer is:
insist
'will have' is the definition.
'insist' can be an answer for 'have' (thesaurus). I'm unsure of the 'will' bit.
'it that sins are absolved in it' is the wordplay.
I cannot quite see how this works, but
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is present in the answer.
an anagram of 'sins' is 'nsis' which is present in the answer.
A single letter 'i' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for insist that I've seen before include "Demand determinedly" , "Press" , "Take a firm stand" , "Maintain strongly" , "express convinced viewpoint" .)