Salad ingredient is shipping hazard (7)
I believe the answer is:
iceberg
This clue is a double definition.
'salad ingredient' is the first definition.
(iceberg lettuce is often used in salads)
'shipping hazard' is the second definition.
(I've seen this in another clue)
'is' acts as a link.
(Other definitions for iceberg that I've seen before include "Titanic sinker - lettuce" , "Main hazard" , "Hazard in Arctic sea" , "sort of lettuce" , "smash hit in Titanic?" .)