Fare in force on odd dates, initially (4)
I believe the answer is:
food
'fare' is the definition.
(thesaurus)
'force on odd dates initially' is the wordplay.
'force' becomes 'f' (symbol used in Physics e.g. f=ma**).
'initially' suggests taking the first letters.
The first letters of 'on odd dates' is 'ood'.
'f'+'ood'='FOOD'
'in' is the link.
(Other definitions for food that I've seen before include "Fast --; -- chain" , "Comestibles" , "Tuck" , "Eats" , "Sustenance" .)