King's wife in dread at sea (6)
I believe the answer is:
edward
'king's' is the definition.
(I've seen this before)
'wife in dread at sea' is the wordplay.
'wife' becomes 'w' (abbreviation).
'in' indicates putting letters inside.
'at sea' indicates anagramming the letters.
'dread' anagrammed gives 'edard'.
'w' inserted inside 'edard' is 'EDWARD'.
(Other definitions for edward that I've seen before include "Former King" , "-- Lear; -- Heath" , "The eighth one abdicated" , "I (1239-1307), II (1284-1327), III (1312-77), IV (1442-83), V (1470-83?), VI (1537-53), VII (1841-1910) or VIII (1894-1972)" , "First name of Mr Rochester (Jane Eyre)" .)