Doctor right about fungal disease (3,3)
I believe the answer is:
dry rot
'fungal disease' is the definition.
'dry rot' can be an answer for 'disease' (dry rot is a kind of health problem). I'm not sure about the 'fungal' bit.
'doctor right about' is the wordplay.
'doctor' becomes 'dr' (synonyms).
'right' becomes 'tory' (I've seen this before).
'about' is a reversal indicator.
'tory' reversed gives 'yrot'.
'dr'+'yrot'='DRY-ROT'
Can you help me to learn more?
(Other definitions for dry rot that I've seen before include "Fungus attacking wood" , "fungal infection" , "Degeneration" , "Wood-destroying fungus" , "housing problem?" .)