What does the cryptic crossword clue "Boat with advanced instrument for making deep soundings (4)" mean?

The wordplay uses a charade (building blocks). TUB (synonym="boat") + A (synonym="advanced") = TUBA The answer is TUBA.

Boat with advanced instrument for making deep soundings (4)

Guardian Cryptic #29354 | 9 Across | 2024-04-11 flower