Nervous man at city section (9)
I believe the answer is:
hyperbola
'section' is the definition.
(I've seen this before)
'nervous man at city' is the wordplay.
I cannot quite understand how this works, but
'man' could be 'hy' and 'hy' is found within the answer.
'city' could be 'la' (Los Angeles) and 'la' is found within the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for hyperbola that I've seen before include "conic section" , "Curve" .)