Cryptic crossword clue
Old flame putting on new outfit for swapping

The most common and most likely answer to this crossword clue is the 10 letter word EXCHANGING

I've seen this crossword clue in Independent
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Buddy explains!

The straight part
We know that "swapping" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case swapping = exchanging.
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 EXCHANGING mean?

EXCHANGING verb
  1. To trade or barter.
  2. To replace with, as a substitute.

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