Show maturity wearing short trousers? (7)
I believe the answer is:
pageant
'show' is the definition.
(a show or display)
'maturity wearing short trousers?' is the wordplay.
'maturity' becomes 'age' (I've seen this before).
'wearing' is an insertion indicator.
'short trousers?' becomes 'pant' (I can't explain this - if you can you should believe this answer much more).
'age' inserted into 'pant' is 'PAGEANT'.
Can you help me to learn more?
(Other definitions for pageant that I've seen before include "Show" , "elaborate display" , "Spectacular parade" , "Extravagant dramatic display" , "Colourful display or parade" .)