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 in another clue)
This is all the clue.
(Other definitions for across that I've seen before include "Transversely" , "Astride" , "Clues like this" , "sort of clue?" , "From side to side of (something)" .)