Sister crossing area by church in shade (6)
I believe the answer is:
nuance
'shade' is the definition.
('nuance' can be a synonym of 'shade')
'sister crossing area by church' is the wordplay.
'sister' becomes 'nun' (I've seen this before).
'crossing' indicates putting letters inside.
'area' becomes 'a' (maths abbreviation).
'by' says to put letters next to each other.
'church' becomes 'ce' (abbreviation for Church of England).
'nun' enclosing 'a' is 'nuan'.
'nuan'+'ce'='NUANCE'
'in' is the link.
(Other definitions for nuance that I've seen before include "Subtlety of meaning" , "Subtle distinction or variation" , "Cue Ann into slight shade" , "Fine shade of meaning" , "A slight shade or trace" .)