Tardy earl keeping time (4)
I believe the answer is:
year
'time' is the definition.
(I know that time can be written as year)
'tardy earl keeping' is the wordplay.
'keeping' indicates the answer is hidden within the clue.
'YEAR' is hidden in the letters of 'tardy earl'.
(Other definitions for year that I've seen before include "Time period" , "One intake of undergrads" , "eg 2004" , "Unit of time" , "One tenth of a decade" .)