Boat with advanced instrument for making deep soundings (4)
I believe the answer is:
tuba
'instrument for making deep soundings' is the definition.
I can't judge whether this definition defines the answer.
'boat with advanced' is the wordplay.
'boat' becomes 'tub' (tub could historically mean a small boat).
'with' is a charade indicator (letters next to each other).
'advanced' becomes 'a' (abbreviation).
'tub'+'a'='TUBA'
Can you help me to learn more?
(Other definitions for tuba that I've seen before include "This loud instrument" , "Valved instrument" , "Brass band instrument" , "Noisy instrument" , "item band might play" .)