VIPs cover undergarments with cardigans, for example (3,5)

I believe the answer is:

top brass

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'vips' is the definition.
(I've seen this before)

I cannot understand how the rest of the clue works.

(Other definitions for top brass that I've seen before include "military leaders" , "Highest-ranking officials with best yellow alloy" , "Important people" , "People in authority (informal)" , "management" .)

I've seen this clue in The Telegraph.

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