Instrument of pain ran God ragged (5,5)
I believe the answer is:
grand piano
'instrument' is the definition.
(grand piano is a kind of instrument)
'pain ran god ragged' is the wordplay.
'ragged' indicates an anagram.
'pain'+'ran'+'god'='painrangod'
'painrangod' anagrammed gives 'GRAND PIANO'.
'of' acts as a link.
(Other definitions for grand piano that I've seen before include "responsible for producing notes ..." , "one getting tickled?" , "Large instrument with horizontal strings" , "maker of notes?" , "One's three-legged" .)