I see diver returning dangerous water feature (7)
I believe the answer is:
iceberg
'dangerous water feature' is the definition.
(danger during a sea voyage)
'i see diver returning' is the wordplay.
'see' becomes 'C' (the word for the letter, according to Chambers).
'diver' becomes 'grebe' (diving bird).
'returning' shows that the letters should be reversed in order.
'grebe' backwards is 'eberg'.
'i'+'c'+'eberg'='ICEBERG'
(Other definitions for iceberg that I've seen before include "Kind of lettuce" , "(Frozen?) type of lettuce" , "Broken piece of a glacier" , "Maritime danger, mostly underwater" , "Largely hidden danger" .)