Intricate patterns in one part of church (8)
I believe the answer is:
transept
'one part of church' is the definition.
('transept' is part of 'church')
'intricate patterns' is the wordplay.
'intricate' is an anagram indicator.
'patterns' anagrammed gives 'TRANSEPT'.
'in' acts as a link.
(Other definitions for transept that I've seen before include "Patterns in part of church at right angle to nave" , "Part of a church - patterns (anag)" , "It crosses the nave in church" , "Arm of church body" , "Part of church intersecting nave" .)