Spiritual number brings in a grand, perhaps (5)
I believe the answer is:
piano
'grand perhaps' is the definition.
(grand is a kind of piano)
'spiritual number brings in a' is the wordplay.
'spiritual' becomes 'pi' (old-fashioned term for 'pious').
'number' becomes 'no' (abbreviation for 'number').
'brings in' means one lot of letters goes inside another.
'pi'+'no'='pino'
'pino' placed around 'a' is 'PIANO'.
(Other definitions for piano that I've seen before include "Opposite of forte" , "Quiet (music)" , "In musical notation, this means softly" , "Keyboard instrument" , "Upright type?" .)