The most common and most likely answer to this crossword clue is the 7 letter word MANDELA
M
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N
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A
More clues leading to the result MANDELA
- Mean lad upset old statesman
- Name inscribed in a medal, prepared for old statesman
- Former president from island meeting endless hold-up
- He led resurgent Africa?
- Famous African person with key blood type
- Nelson, servant of the French?
- E.g. Horatio de la Nelson?
- Chap was the leader, coming over and heading for Admiral Nelson
- African giant contrived to annex northern city
- Nelson lengthily detained ship of the French
Buddy explains!

The straight part
We know that "Nelson lengthily detained" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case nelson lengthily detained = mandela.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.