Decrease metal that ferryboat contains in the beginning (4)
I believe the answer is:
iron
This could be a double definition.
'decrease' is the first definition.
(de-crease: remove creases by ironing)
'metal that ferryboat contains in the beginning' is the second definition.
'iron' can be an answer for 'metal' (iron is a kind of metal). I'm not certain of the rest of the definition.
Can you help me to learn more?
(Other definitions for iron that I've seen before include "1 down, symbol Fe" , "Metal - press" , "Decrease" , "Smoother - metal" , "Smooth - driver?" .)