Noel Coward play about Glen arresting villain (9)
I believe the answer is:
cavalcade
'noel coward play' is the definition.
I can't tell whether this definition defines the answer.
'about glen arresting villain' is the wordplay.
'about' becomes 'ca' (short for circa).
'glen' becomes 'vale' (both can mean a type of valley).
'arresting' means one lot of letters goes inside another.
'villain' becomes 'cad' (cad can mean a nasty person).
'vale' going around 'cad' is 'valcade'.
'ca'+'valcade'='CAVALCADE'
Can you help me to learn more?
(Other definitions for cavalcade that I've seen before include "Column or procession of riders" , "Procession of people riding" , "Ceremonial procession, of horses say" , "Procession on horseback or in cars" .)