Condition like this that's avoided is case of malaria (6)
I believe the answer is:
asthma
'condition' is the definition.
(asthma is a kind of condition)
'like this that's avoided is case of malaria' is the wordplay.
'like' becomes 'as'.
'this that's avoided' becomes 'th' (I can't explain this - if you can you should give a lot more credence to this answer).
'is case of' says to hollow out the word (remove centre letters) (outsides of).
'malaria' with its centre removed is 'ma'.
'as'+'th'+'ma'='ASTHMA'
Can you help me to learn more?
(Other definitions for asthma that I've seen before include "Breathing complaint" , "Bronchial allergy" , "Breathing illness" , "Mat has difficult breathing" , "Respiratory disease" .)