The most common and most likely answer to this crossword clue is the 11 letter word SUBORDINATE
I've seen this crossword clue in Independent
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More clues leading to the result SUBORDINATE
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The straight part
We know that "assistant" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case assistant = subordinate.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 SUBORDINATE mean?
SUBORDINATE noun- One who is subordinate.
- To make subservient.
- To treat as of less value or importance.
- To make of lower priority in order of payment in bankruptcy.
- Placed in a lower class, rank, or position.
- Submissive or inferior to, or controlled by authority.
- (grammar, of a clause) dependent on and either modifying or complementing the main clause
- Descending in a regular series.