4d Be tough you'll need to do this if you go shark-fishing (4,1,6,4)
?A?E A S?R?N" ??N?
25a Leave the dessert (5)
S???T
The middle letter of the 25a is the first letter of the last word in 4d
16a Suffocating atmosphere that's always drifting around the harbour (6)
R?F??E
Thanks in anticipation!