Charm of sea in fact being at sea! (9)
I believe the answer is:
fascinate
'charm' is the definition.
('fascinate' can be a synonym of 'charm')
'sea in fact being at sea' is the wordplay.
'being at sea' indicates an anagram.
'sea'+'in'+'fact'='seainfact'
'seainfact' with letters rearranged gives 'FASCINATE'.
'of' acts as a link.
(Other definitions for fascinate that I've seen before include "Captivate" , "Enchant - beguile" , "Intrigue" , "Irresistibly interest" , "Engage admiring attention of" .)