A sweet one can be both sound and hot! (5)
I believe the answer is:
Here is my best explanation:
'a sweet' is the definition.
'sound and hot' is the wordplay.
'sound' becomes 'toot' (toot is a kind of sound**).
'and' means one lot of letters go next to another.
'hot' becomes 'h'.
'one can be both' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
(Other definitions for tooth that I've seen before include "Canine, for example", "Gearwheel projection", "Gearwheel cog", "In which the old are long", "Biter", "piece", "Eg, molar", "Taste", "It erupts" and "Cog".)