Trouble with stern on vessel (8)
I believe the answer is:
hardship
'trouble' is the definition.
(I know that hardship is a type of bad luck)
'stern on vessel' is the wordplay.
'stern' becomes 'hard' (I've seen this in another clue).
'on' says to put letters next to each other.
'vessel' becomes 'ship' (ship is a kind of vessel).
'hard'+'ship'='HARDSHIP'
'with' acts as a link.
(Other definitions for hardship that I've seen before include "Privation difficult to endure" , "Severe discomfort or deprivation" , "Need" , "Severe difficulty or suffering" , "distress" .)