Charlie in riotous romcom is miniature model (9)
I believe the answer is:
microcosm
'miniature model' is the definition.
'microcosm' can be an answer for 'model' (microcosm is a kind of model). I am not sure about the 'miniature' bit.
'charlie in riotous romcom is' is the wordplay.
'charlie' becomes 'C' (phonetic alphabet: alpha, bravo, charlie etc.).
'in' indicates putting letters inside.
'riotous' is an anagram indicator.
'romcom'+'is'='romcomis'
'romcomis' anagrammed gives 'mirocosm'.
'c' inserted within 'mirocosm' is 'MICROCOSM'.
Can you help me to learn more?
(Other definitions for microcosm that I've seen before include "Miniature encapsulation of something much larger" , "World in miniature" , "Miniature representation of a larger entity" , "Miniature encapsulation of the bigger picture" , "Miniature example" .)