Float boat (6)
I believe the answer is:
launch
I believe this clue is a double definition.
'float' is the first definition.
(I know that float is a kind of launch)
'boat' is the second definition.
(launch is a kind of boat)
(Other definitions for launch that I've seen before include "Embark" , "Send off (a rocket)" , "(Send) motor-boat (into the water)" , "Craft - project" , "starter?" .)