Commander-in-Chief must arrest poor inmate filming? (9)
I believe the answer is:
cinematic
'filming?' is the definition.
'commander-in-chief must arrest poor inmate' is the wordplay.
'commander-in-chief' becomes 'cic'.
'must arrest' indicates putting letters inside.
'poor' is an anagram indicator.
'inmate' with letters rearranged gives 'inemat'.
'cic' going around 'inemat' is 'CINEMATIC'.
(Other definitions for cinematic that I've seen before include "production fit for the screen" , "In movie" , "Relating to the silver screen" , "Relating to film" , "such entertainments" .)