Heard boy notice solar feature (7)
I believe the answer is:
sunspot
'solar feature' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'heard boy notice' is the wordplay.
'heard' shows a homophone (sound like).
'boy' becomes 'son' ('son' can be a synonym of 'boy').
'notice' becomes 'spot' (I've seen this before).
'son' is a homophone of 'sun'.
'sun'+'spot'='SUNSPOT'
Can you help me to learn more?
(Other definitions for sunspot that I've seen before include "Solar dark patch" , "holiday resort" , "Dark cool patch on the surface of our nearest star" , "warm place" , "relatively dark situation" .)