A trying time or transaction (6)
I believe the answer is:
ordeal
'a trying time' is the definition.
(I've seen this in another clue)
'or transaction' is the wordplay.
'transaction' becomes 'deal' (a deal is a transaction or exchange).
'or'+'deal'='ORDEAL'
(Other definitions for ordeal that I've seen before include "Unpleasant and prolonged experience" , "A tough time or hardship" , "Severly trying experience" , "A difficult and harrowing experience" , "Severely trying experience" .)