So is heard complaining (4)
I believe the answer is:
sick
'complaining' is the definition.
Both the definition and answer are adjectives. Perhaps they are linked in a way I don't understand?
'so is heard' is the wordplay.
'so' becomes 'sic' ('sic' is 'so' in Latin).
'is heard' indicates a 'sounds like' (homophone) clue.
'sic' is a homophone of 'SICK'.
Can you help me to learn more?
(Other definitions for sick that I've seen before include "not good" , "Infirm" , "Poorly" , "well? Hardly" , "Ill; perverted" .)