The most common and most likely answer to this crossword clue is the 11 letter word ALTERNATION
A
L
T
E
R
N
A
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Buddy explains!

The straight part
We know that "Interchange" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case interchange = alternation.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 ALTERNATION mean?
ALTERNATION noun- The reciprocal succession of (normally two) things in time or place; the act of following and being followed by turns; alternate succession, performance, or occurrence
- The response of the congregation speaking alternately with the minister.
- Ablaut.
- A pattern by which more than one construct is possible, as with "Alice cooked Bob dinner" and "Alice cooked dinner for Bob".
- The "inclusive or" truth function.
- A sequence that alternates between positive and negative values; sometimes incorrectly used to mean permutation.
- A construct in a regular expression that can match any of several specified subexpressions.
- A type of partial truncation of a polygon, polyhedron or tiling in which alternate vertices are removed.