Tablet lost in Sussex town (6)
I believe the answer is:
battle
'sussex town' is the definition.
(I've seen this before)
'tablet lost' is the wordplay.
'lost' indicates anagramming the letters.
'tablet' is an anagram of 'BATTLE'.
'in' is the link.
(Other definitions for battle that I've seen before include "Sustained conflict" , "Ben < 's engagement" , "Struggle tenaciously" , "war" , "'The race is not to the swift, nor the ... to the strong'" .)