Boat returning from a fruitless event (6)
I believe the answer is:
vessel
'boat' is the definition.
(thesaurus)
'returning from a fruitless event' is the wordplay.
'returning' is a reversal indicator.
'from' indicates a hidden word.
'lessev' can be found hidden inside 'fruitless event'.
'lessev' reversed gives 'VESSEL'.
(Other definitions for vessel that I've seen before include "Watercraft or water container" , "Kind of ship or a kitchen pot (6)" , "Ship, or receptacle for liquid" , "Container for liquid or craft for water" , "Craft for water transportation" .)