Old Greek is real worried about baby (9)
I believe the answer is:
aristotle
'old greek' is the definition.
'Aristotle' can be an answer for 'greek' (Aristotle is an example). I'm not sure about the 'old' bit.
'is real worried about baby' is the wordplay.
I cannot really see how this works, but
'is' is within the answer.
'real' could be 'e' (e is a kind of real) and 'e' is present in the answer.
'about' could be 'a' (abbreviation in Chambers) and 'a' is present in the answer.
'baby' could be 'tot' (I've seen this in another clue) and 'tot' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for aristotle that I've seen before include "noted thinker" , "Great Greek philosopher of 4th century B.C." , "polymath" , "Thinking Greek" , "Ancient Athenian philosopher, pupil of Plato" .)