Show age in a symptom of exhaustion (7)
I believe the answer is:
pageant
'show' is the definition.
(a show or display)
'age in a symptom of exhaustion' is the wordplay.
'in' means one lot of letters goes inside another.
'a symptom of exhaustion' becomes 'pant' (I can't justify this - if you can you should believe this answer much more).
'age' going into 'pant' is 'PAGEANT'.
Can you help me to learn more?
(Other definitions for pageant that I've seen before include "Scene moving" , "Neat gap for colourful spectacle" , "Dramatic performance" , "Spectacular display" , "Elaborate procession on historical theme" .)