Take off in boat (6)
I believe the answer is:
launch
I believe this is a double definition.
'take off' is the first definition.
(eg a rocket taking off or launching)
'boat' is the second definition.
(launch is a kind of boat)
'in' is the link.
(Other definitions for launch that I've seen before include "Send out; motor boat" , "Start - motor-driven boat" , "Set (a boat) afloat" , "Send on its course, new ship or publication" , "Send off (a rocket)" .)