The most common and most likely answer to this crossword clue is the 7 letter word PLODDER
I've seen this crossword clue in Financial Times
P
L
O
D
D
E
R
Buddy explains!

The straight part
We know that "One moves laboriously" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one moves laboriously = plodder.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 PLODDER mean?
PLODDER noun- One who plods.
- A person who works slowly, making a great effort with little result; a person who studies laboriously.