Note in scale, only not E (3)
I believe the answer is:
'note' is the definition.
(I've seen this in another clue)
'scale only not e' is the wordplay.
'scale' becomes 's' (this could be a standard abbreviation which I don't know about).
'only' becomes 'sole' (synonyms).
'not' suggests deleting specific letters.
'e' becomes 'Es' (synonyms).
'sole' with 'es' removed is 'ol'.
'in' is the link.
Can you help me to learn more?
(Other definitions for sol that I've seen before include "Roman counterpart of Helios" , "Note, old french coin" , "The sun in 12 Across" , "Personification of the sun" , "Note - colloid - the Sun" .)