Unfortunate -- splashed endlessly around (7)
I believe the answer is:
hapless
'unfortunate' is the definition.
('hapless' can be similar in meaning to 'unfortunate')
'splashed endlessly around' is the wordplay.
'endlessly' means to remove the last letter.
'around' indicates an anagram.
'splashed' with its last letter removed is 'splashe'.
'splashe' is an anagram of 'HAPLESS'.
(Other definitions for hapless that I've seen before include "Piteous" , "Ill-starred" , "Pathetic" , "He slaps (anag) - unlucky" , "Ill-fated" .)