Rested for a day (3)
I believe the answer is:
sat
This clue is a double definition.
'rested' is the first definition.
(to sit is to rest)
'day' is the second definition.
(abbreviation for Saturday)
'for a' acts as a link.
(Other definitions for sat that I've seen before include "Posed (for an artist)" , "Used a chair" , "nearly half a day" , "Took a seat and posed for a portrait" , "Perched" .)