Trial or transaction (6)
I believe the answer is:
ordeal
'trial' is the definition.
(I've seen this before)
'or transaction' is the wordplay.
'transaction' becomes 'deal' (deal is a kind of transaction).
'or'+'deal'='ORDEAL'
(Other definitions for ordeal that I've seen before include "Difficult experience, a tough time" , "Tribulation" , "very hard test" , "Horrible experience" , "A test of endurance or or difficult experience" .)