Jellyfish found in Mediterranean and America (6)
I believe the answer is:
medusa
'jellyfish' is the definition.
('medusa' can be a synonym of 'jellyfish')
'mediterranean and america' is the wordplay.
'mediterranean' becomes 'med' (I've seen this in other clues).
'and' says to put letters next to each other.
'america' becomes 'usa' ('U.S.A.' can be a synonym of 'america').
'med'+'usa'='MEDUSA'
'found in' acts as a link.
(Other definitions for medusa that I've seen before include "Monster" , "One of three sisters with snakes for hair" , "Amused by the mythical gorgon?" , "Gorgon with snakes for hair" , "Hideous female" .)