Sauce boat now costing more (7)
I believe the answer is:
ketchup
'sauce' is the definition.
(ketchup is a type of sauce)
'boat now costing more' is the wordplay.
I cannot really see how this works, but
'boat' could be 'ketch' (ketch is a type of sailing boat) and 'ketch' is found within the answer.
The remaining letters 'up' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for ketchup that I've seen before include "Red sauce" , "Condiment" , "Relish" , "Spicy tomato sauce" , "Thick sauce, with tomatoes" .)