One must vacate seat daily (4)
I believe the answer is:
char
'daily' is the definition.
(both can mean a cleaner)
'one must vacate seat' is the wordplay.
'one' becomes 'i' (Roman numeral).
'must vacate' suggests deleting specific letters.
'seat' becomes 'chair' (chair is a kind of seat).
'chair' with 'i' taken out is 'CHAR'.
(Other definitions for char that I've seen before include "Overcook - fish - daily" , "Scorch, small fish" , "Make black by burning, or a small trout" , "Scorch - fish - cleaning lady" , "Blacken by burning" .)