What does the cryptic crossword clue "Romans managed to capture a galley slave (7)" mean?

The definition is "galley slave". The wordplay uses an anagram. anagram of ROMANS + A = OARSMAN; definition: "galley slave" The answer is OARSMAN.

Romans managed to capture a galley slave (7)

Daily Mail Cryptic #16851 | 9 Across | 2022-06-03 flower