Illness inland may trouble when last operation cancelled (6)
I believe the answer is:
malady
'illness' is the definition.
(synonyms)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for malady that I've seen before include "Sickness or disease" , "affection" , "Complaint" , "Illness or disease" , "Disease, ailment" .)