Cleric has key to ocean travel (6)
I believe the answer is:
deacon
'cleric' is the definition.
(I've seen this before)
'key to ocean travel' is the wordplay.
'key' becomes 'd' (I've seen this in other clues).
'travel' indicates an anagram (I've seen 'travelling' mean this).
'ocean' with letters rearranged gives 'eacon'.
'd'+'eacon'='DEACON'
'has' is the link.
(Other definitions for deacon that I've seen before include "A member of the lower orders of clergy" , "Churchman" , "Church officer" , "Church post" , "Clergyman of low rank" .)