What does the cryptic crossword clue "Raft with hole initially lost at sea — not one of these then? (7)" mean?

The wordplay uses acrostic. anagram of RAFT (synonym="RAFT") + OLE (synonym="OLE") = FLOATER The answer is FLOATER.

Raft with hole initially lost at sea — not one of these then? (7)

Guardian Cryptic #29152 | 1 Across | 2023-08-18 flower