Sea found by fish, unusually lucky (7)
I believe the answer is:
charmed
'unusually lucky' is the definition.
(I've seen this before)
'sea found by fish' is the wordplay.
'sea' becomes 'med' (abbreviation of Mediterranean).
'found by' says to put letters next to each other.
'fish' becomes 'char' (char is a kind of fish**).
'med' put after 'char' is 'CHARMED'.
(Other definitions for charmed that I've seen before include "Entranced" , "blessed by fortune" , "Unusually lucky" , "Enchanted" .)