In tanning area, drop cap and loosen tie (7)

I believe the answer is:

unstrap

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

I can't explain the remainder of the clue.

(Other definitions for unstrap that I've seen before include "Remove fastenings from" , "Release" , "loose" , "Loosen tie" .)

I've seen this clue in The Sunday Times and The Times.

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