Grand, perhaps sanctimonious article by Oscar (5)
I believe the answer is:
piano
'grand perhaps' is the definition.
(grand is a kind of piano)
'sanctimonious article by oscar' is the wordplay.
'sanctimonious' becomes 'pi'.
'article' becomes 'an' (indefinite article).
'by' is a charade indicator (letters next to each other).
'oscar' becomes 'o' (phonetic alphabet: alpha, bravo, charlie etc.).
'pi'+'an'+'o'='PIANO'
(Other definitions for piano that I've seen before include "Clavier" , "Soft, softly (music)" , "Musical instrument - play quietly" , "In musical notation, this means softly" , "In music, soflty" .)