Professional initially given no sibling's forecast of disease's outcome (9)

I believe the answer is:

prognosis

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'forecast of disease's outcome' is the definition.
'prognosis' can be an answer for 'forecast' (synonyms). I am unsure of the 'of disease's outcome' bit.

'professional initially given no sibling's' is the wordplay.
'professional' becomes 'pro' (abbreviation).
'initially' suggests taking the first letters.
'sibling' becomes 'sis' (short for sister).
The first letter of 'given' is 'g'.
'pro'+'g'+'no'+'sis'='PROGNOSIS'

Can you help me to learn more?

(Other definitions for prognosis that I've seen before include "Medical opinion" , "Medical prediction" , "Forecast, outlook" , "Forecast of course of illness as by doctor" , "Prediction as to how something will turn out" .)

I've seen this clue in The Daily Express.

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