Remove periods last in timetable (5)
I believe the answer is:
erase
'remove' is the definition.
(to erase is to remove)
'periods last in timetable' is the wordplay.
'periods' becomes 'eras' (era is a kind of period).
'last in' indicates one should take the final letters.
The final letter of 'timetable' is 'e'.
'eras'+'e'='ERASE'
(Other definitions for erase that I've seen before include "Blot out" , "Rub out, expunge" , "Obliterate" , "Efface" , "Eradicate" .)