Tardy getting into bed (7)
I believe the answer is:
belated
'tardy' is the definition.
(synonyms)
'getting into bed' is the wordplay.
'getting' becomes 'late' (I am not sure about this - if you are sure you should believe this answer much more).
'into' is an insertion indicator.
'late' going into 'bed' is 'BELATED'.
Can you help me to learn more?
(Other definitions for belated that I've seen before include "Coming after time" , "Behind time" , "Out of date" , "Bleated, being too late" , "Coming too late" .)