Fixed ahead of time (4)
I believe the answer is:
fast
I believe this is a double definition.
'fixed' is the first definition.
(synonyms)
'ahead of time' is the second definition.
(similar in meaning)
(Other definitions for fast that I've seen before include "Of clock, ahead of correct time" , "Moving quickly" , "Relating to the mind" , "sort of convenience food" , "Starve; quick" .)