The most common and most likely answer to this crossword clue is the 9 letter word DEPUTISED
I've seen this crossword clue in The Times
D
E
P
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T
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D
More clues leading to the result DEPUTISED
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The straight part
We know that "Was standing in" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case was standing in = deputised.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 DEPUTISED mean?
DEPUTISED verb- To make (someone) a deputy; to officially empower.
- To make or name as a substitute.
- To act as a deputy.