Attacked by a jellyfish (5)
I believe the answer is:
stung
'attacked by a jellyfish' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for stung that I've seen before include "Wounded by, eg, bee" , "Peeved" , "Punctured eg by wasp" , "Taken for a ride" , "Aroused to impatience or anger" .)