A boy enthralled by my illness (6)
I believe the answer is:
malady
'illness' is the definition.
(malady is a kind of health problem)
'a boy enthralled by my' is the wordplay.
'a boy' becomes 'al'.
'enthralled by' is an insertion indicator ('enthral' can mean 'capture').
'my' becomes 'mady' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'al' placed into 'mady' is 'MALADY'.
Can you help me to learn more?
(Other definitions for malady that I've seen before include "Sickness, ailment" , "Sickness or disease" , "Afflication" , "affection" , "Complaint" .)