He became aware of the gravity of the apple situation (5,6)
I believe the answer is:
isaac newton
'he became aware of the gravity of the apple situation' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'he' is the wordplay.
I cannot quite see how this works, but
'he' could be 'newton' and 'newton' is found within the answer.
The remaining letters 'isaac' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for isaac newton that I've seen before include "English mathematician and physicist" , "Lawmaker" , "Principia author" , "he described it mathematically" , "Seventeenth to eighteenth century English physicist/mathematician" .)