Essential fact jurors missed from one side to the other (6)
I believe the answer is:
across
'from one side to the other' is the definition.
(I've seen this before)
I cannot understand how the remainder of the clue works.
(Other definitions for across that I've seen before include "what follows one here" , "From one side to another" , "From side to side of (something)" , "Astride" , "written like this?" .)