The most common and most likely answer to this crossword clue is the 8 letter word MAGELLAN
I've seen this crossword clue in The Sunday Telegraph
M
A
G
E
L
L
A
N
More clues leading to the result MAGELLAN
- One learned all about northern explorer
- A good measure introduced by fellow who went on long expedition?
- Manage somehow to traverse two lakes as navigator
- Publication number 12’s about lecturer and explorer
- Chap taking on legal manoeuvring, straight-talking fellow?
- Navigator chap welcomes legal wrangling
- Chap introducing legal reform he explored at great length
- Explorer retired in final leg – America
- Explorer and crew taking a set line
Buddy explains!
The straight part
We know that "he explored at great length" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case he explored at great length = magellan.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.