Child born with temperature raised by a German (9)
I believe the answer is:
tweenager
'child' is the definition.
(I have seen 'Precocious child' mean 'tweenager' so perhaps 'child' could also mean 'tweenager')
'born with temperature raised by a german' is the wordplay.
'born' becomes 'nee' ('nee' is 'born' in French).
'with' becomes 'w' (short for with).
'temperature' becomes 't' (abbreviation).
'raised by' says the letters should be written in reverse.
'german' becomes 'ger' (abbreviation).
'nee'+'w'+'t'='neewt'
'neewt' reversed gives 'tween'.
'tween'+'a'+'ger'='TWEENAGER'
(Other definitions for tweenager that I've seen before include "Precocious child" , "Possibly a ten-year-old" , "adolescent" , "exasperating twelve-year-old" , "(Informally) a child approaching the age of 13?" .)