The most common and most likely answer to this crossword clue is the 4 letter word VEEP
V
E
E
P
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The straight part
We know that "Deputy" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case deputy = veep.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 VEEP mean?
VEEP noun- (US politics) The Vice President of the United States; the office of Vice President of the United States, especially during an election cycle where several are in the running for the nomination.
- Any vice president (in a corporation, organization, etc.)