Secure offshore (6)
I believe the answer is:
moored
'secure offshore' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for moored that I've seen before include "Made fast" , "Fastened with a line or anchored" , "Of boat, secured by rope to shore" , "Tied up to berth like ship or boat" , "Of boat, tied up or secured" .)