Furs bought principally in auctions (6)

I believe the answer is:

sables

'furs' is the definition.
(sable is a kind of fur)

'bought principally in auctions' is the wordplay.
'principally' indicates taking the first letters.
'in' is an insertion indicator.
'auctions' becomes 'sales' (I've seen this before).
The initial letter of 'bought' is 'b'.
'b' going within 'sales' is 'SABLES'.

(Another definition for sables that I've seen is " Small black animals with fine fur".)

I've seen this clue in The Telegraph.

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