21 across
Sounds
essential
but
cut
short,
I
see
(5)
Sounds essential but cut short, I see (5)
hints
0
checks
0
hints
The definition is at the beginning of the clue.
How the clue works
Sounds is the definition, meaning music. The wordplay builds the answer in three parts: "must" (something essential) is "cut short" by dropping its last letter to give MUS, then "I" gives I, and "see" gives C (the letter C sounds like "see"). Put them together and you get MUSIC.