Solution for 7 June cryptic crossword clue

Transport on the polar shelf (6)

Solution – sledge

This is a "literally so" clue.  The whole clue can be taken to mean "sledge" as well as being able to break the clue up into its constituent parts.

Sledges were used as transport on the polar shelf

They are also a more general form of transport

And "polar" is also either "n" or "s" for north or south.  In this case if you add a word for "shelf" ie "ledge" to s, you get "sledge".

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