A burden 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)
'a burden' is the wordplay.
'burden' becomes 'cross' (someone's particular burden is their cross).
'a'+'cross'='ACROSS'
(Other definitions for across that I've seen before include "...this is 'Number Ten'" , "sort of clue?" , "Transversely" , "Unlike this clue" , "As this is entered" .)