Shade sister found outside a church (6)
I believe the answer is:
nuance
'shade' is the definition.
(I know that shade can be written as nuance)
'sister found outside a church' is the wordplay.
'sister' becomes 'nun' (nuns are referred to as sister).
'found outside' means one lot of letters goes inside another.
'church' becomes 'CE' (abbreviation for Church of England).
'nun' placed around 'a' is 'nuan'.
'nuan'+'ce'='NUANCE'
(Other definitions for nuance that I've seen before include "Subtle shade of difference" , "Fine distinction" , "Delicate shade of meaning" , "Subtlety, nicety" , "Subtlety of meaning" .)