Undersea craft permitted to be rented out again (6)
I believe the answer is:
sublet
'be rented out again' is the definition.
(let out again)
'undersea craft permitted' is the wordplay.
'undersea craft' becomes 'sub' (I've seen this in another clue).
'permitted' becomes 'let' (to let something happen is to permit it).
'sub'+'let'='SUBLET'
'to' acts as a link.
(Other definitions for sublet that I've seen before include "Rent out what one has rented" , "Rent out to a third party" , "Lease all or part of a rented property to another" , "get help to pay the rent, maybe" , "Rent all or part of a rented property to another person" .)