Limited volume restricting one old instrument (4)
I believe the answer is:
viol
'old instrument' is the definition.
(historical stringed instrument)
'limited volume restricting one' is the wordplay.
'limited volume' becomes 'vol' (abbreviation; 'limited' indicates a short form).
'restricting' means one lot of letters goes inside another.
'one' becomes 'i' (Roman numeral).
'vol' placed around 'i' is 'VIOL'.
(Other definitions for viol that I've seen before include "Precursor of the violin" , "Early fiddle" , "something from the past to play" , "Old string instrument" , "Early bowed stringed instrument" .)