Trying experience in old wood across river (6)
I believe the answer is:
ordeal
'trying experience' is the definition.
(I've seen this before)
'old wood across river' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'wood' becomes 'deal' (deal is a kind of wood**).
'across' is an insertion indicator.
'river' becomes 'r'.
'o'+'deal'='odeal'
'odeal' going around 'r' is 'ORDEAL'.
'in' is the link.
(Other definitions for ordeal that I've seen before include "Severly trying experience" , "Prolonged distressing experience" , "trying affair" , "Trial; nightmare" , "Prolonged suffering, difficult to endure" .)