Tardy putting the old in bed (7)
I believe the answer is:
belated
'tardy' is the definition.
('belated' can be a synonym of 'tardy')
'the old in bed' is the wordplay.
'the old' becomes 'late' (I've seen this in other clues).
'in' indicates putting letters inside.
'late' inserted within 'bed' is 'BELATED'.
'putting' acts as a link.
(Other definitions for belated that I've seen before include "Out of date" , "Tardy" , "Bleated, being overdue" , "Coming after time" , "After the proper time" .)