Ailment of baby repelled by surgery (8)
I believe the answer is:
smallpox
'ailment' is the definition.
The definition and answer can be both states of affairs as well as being singular nouns.
Maybe you can see a link between them that I can't see?
'baby repelled by surgery' is the wordplay.
'baby' becomes 'small'.
'repelled' is a reversal indicator.
'by' becomes 'x' (multiplication sign).
'surgery' becomes 'op' (short for operation).
'x'+'op'='xop'
'xop' backwards is 'pox'.
'small'+'pox'='SMALLPOX'
'of' acts as a link.
Can you help me to learn more?
(Other definitions for smallpox that I've seen before include "Viral disease, now almost eradicated by vaccination" , "Highly contagious viral disease with fever and skin pustules that leave permanent scars" , "Acute viral disease, technical name variola" .)