Cryptic crossword clue
Take off underclothing, finding impurities 7

The most common and most likely answer to this crossword clue is the 7 letter word DOPANTS

I've seen this crossword clue in The Guardian
D
O
P
A
N
T
S

Buddy explains!

The straight part
We know that "impurities" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case impurities = dopants.
The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.
This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.

What does DOPANTS mean?

DOPANTS noun
  1. A substance added in small amounts to a pure material, such as semiconductor, to alter its original electrical or optical properties; a doping agent

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