Ready to accept old Stone's comeback (7)
I believe the answer is:
riposte
'comeback' is the definition.
('riposte' can be a synonym of 'comeback')
'ready to accept old stone's' is the wordplay.
'ready' becomes 'ripe' ('ripe' can be similar in meaning to 'ready'**).
'to accept' is an insertion indicator.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'stone' becomes 'st'.
'o'+'st'='ost'
'ripe' going around 'ost' is 'RIPOSTE'.
(Other definitions for riposte that I've seen before include "Counter-thrust" , "Smart reply" , "Rejoinder" , "Quick retort or return thrust in fencing" , "Fencer's counterattack" .)