Everything's bound to go round — that's agreed (7)
'agreed' is the definition.
('tally' can be a synonym of 'agree')
'everything's bound to go round' is the wordplay.
'everything' becomes 'all' (I've seen this before).
'bound' becomes 'tied' ('tie' can be a synonym of 'bind').
'to go round' indicates putting letters inside.
'all' put into 'tied' is 'TALLIED'.
'that's' is the link.
(Other definitions for tallied that I've seen before include "Reckoned debt or score", "Corresponded - kept score", "Matched", "Agreed, corresponded", "Agreed; calculated".)