Suffering tough on vessel (8)
I believe the answer is:
hardship
'suffering' is the definition.
(I've seen this before)
'tough on vessel' is the wordplay.
'tough' becomes 'hard' (similar in meaning).
'on' is a charade indicator (letters next to each other).
'vessel' becomes 'ship' (ship is a kind of vessel).
'hard'+'ship'='HARDSHIP'
(Other definitions for hardship that I've seen before include "Adversity, affliction" , "difficult to take" , "Severe discomfort, a tough time" , "Severe privation or suffering" , "difficult situation" .)