Nothing quartet recalled about old instrument (6)
I believe the answer is:
violin
'instrument' is the definition.
(violin is a kind of instrument)
'nothing quartet recalled about old' is the wordplay.
'nothing' becomes 'nil' ('nil' can be a synonym of 'nothing'**).
'quartet' becomes 'iv' (roman numerals for four).
'recalled' shows that the letters should be reversed in order.
'about' is an insertion indicator.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'nil'+'iv'='niliv'
'niliv' back-to-front is 'vilin'.
'vilin' going around 'o' is 'VIOLIN'.
(Other definitions for violin that I've seen before include "A stringed musical instrument, say a Stradivarius" , "Bowed instrument" , "An elevated fiddle" , "Instrument with four strings" , "Nigel Kennedy instrument" .)