Alias Sol, note (3)
I believe the answer is:
soh
'note' is the definition.
(a note in the do-re-mi system)
'alias sol' is the wordplay.
I cannot quite see how this works, but
'sol' could be 'so' (synonyms) and 'so' is present in the answer.
A single letter 'h' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for soh that I've seen before include "Musical note; sounds like very good" , "Note of major scale" , "It's between fah and la" , "element of scale" , "It comes between fah and lah" .)