Get in boat at sea (6)
I believe the answer is:
obtain
'get' is the definition.
(I know that get can be written as obtain)
'in boat at sea' is the wordplay.
'at sea' is an anagram indicator.
'in'+'boat'='inboat'
'inboat' is an anagram of 'OBTAIN'.
(Other definitions for obtain that I've seen before include "Get or lay hold of" , "Get - secure" , "Hold good" , "Get or receive" , "Acquire or procure" .)