Pronounce fit (5)
I believe the answer is:
sound
I believe this clue is a double definition.
'pronounce' is the first definition.
(sounding is a kind of pronouncing)
'fit' is the second definition.
(associated in meaning)
(Other definitions for sound that I've seen before include "Valid" , "Not diseased or damaged - listen" , "Fathom" , "Health - noise" , "stretch of water" .)