German crew supporting the stern of ferry boat (5)
I believe the answer is:
yacht
'boat' is the definition.
(yacht is a type of boat)
'german crew supporting the stern of ferry' is the wordplay.
'german crew' becomes 'acht' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'supporting' means one lot of letters go next to another (in a down clue, some letters go below others).
'the stern of' says to take the final letters (stern can mean back).
The final letter of 'ferry' is 'y'.
'acht' put after 'y' is 'YACHT'.
Can you help me to learn more?
(Other definitions for yacht that I've seen before include "Type of boat" , "Cathy (anag.)" , "Pleasure-boat" , "Light sailing-vessel for sport" , "Fast sailing vessel" .)