Variety of salad vegetable -- only its tip’s usually taken in (7)

I believe the answer is:

iceberg

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'variety' is the definition.
(I have seen 'Variety of lettuce' mean 'iceberg' so perhaps 'variety' could also mean 'iceberg')

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for iceberg that I've seen before include "that has hidden depths?" , "(Frozen?) type of lettuce" , "Main hazard" , "shunned by sailors?" , "Arctic shipping hazard" .)

I've seen this clue in The Telegraph.

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