Note that starts off the dawn chorus (3)
I believe the answer is:
'note' is the definition.
(I know that sol is a type of note)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for sol that I've seen before include "The sun in Spain" , "Note; Peruvian currency" , "nearby star" , "Fifth note of scale" , "Spanish and poetic sun" .)