It requires a truly consistent performance from its cast (9)
I believe the answer is:
docudrama
'it requires a truly consistent' is the definition.
The definition suggests a singular noun which matches the answer.
'performance from its cast' is the wordplay.
I cannot quite see how this works, but
'performance' could be 'drama' (I have seen 'Theatrical performance ' mean 'drama' so perhaps 'performance' could also mean 'drama') and 'drama' is found within the answer.
'from' could be 'o' (I've seen this in other clues) and 'o' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for docudrama that I've seen before include "TV play based on real events" , "Dramatised TV programme based on real events" , "realistic fiction" , "sort of play" .)