People staying dry without a bit of clothing in scripture (6)
I believe the answer is:
avesta
'scripture' is the definition.
(scripture in Zoroastrianism)
'people staying dry without a bit of clothing' is the wordplay.
'people staying dry' becomes 'AA' (Alcoholics Anonymous).
'without' indicates putting letters inside ('without' can be similar in meaning to 'outside').
'a bit of clothing' becomes 'vest' (type of item of clothing).
'aa' enclosing 'vest' is 'AVESTA'.
'in' acts as a link.
(Other definitions for avesta that I've seen before include "holy scriptures" , "holy text" , "Parsee scriptures" , "sacred text" , "collection of sacred writings" .)