In preference to grand, a new instrument for the church (5)
I believe the answer is:
organ
'new instrument for the church' is the definition.
I can't tell whether this definition defines the answer.
'in preference to grand a' is the wordplay.
'in preference' becomes 'or' (I can't justify this - if you can you should believe this answer much more).
'to grand' becomes 'g' (G is short for grand as in a thousand).
'a' becomes 'an'.
'or'+'g'+'an'='ORGAN'
Can you help me to learn more?
(Other definitions for organ that I've seen before include "Functional part of body" , "Perhaps one that's stopped" , "Eg, heart/liver" , "May be in the loft" , "Soft part of the body which has a specific function" .)