Working title of film oddly omitted recurring theme (9)
I believe the answer is:
leitmotif
'recurring theme' is the definition.
(recurring idea or image in a creative work)
'working title of film oddly omitted' is the wordplay.
'working' indicates an anagram.
'oddly omitted' means one should take alternating letters (letters in odd-numbered positions removed).
The alternating letters of 'film' are 'im'.
'title'+'of'+'im'='titleofim'
'titleofim' with letters rearranged gives 'LEITMOTIF'.
(Other definitions for leitmotif that I've seen before include "A melodic phrase that accompanies the reappearance of a person on stage" , "Recurring theme in literary composition" , "it's a repetitive strain" , "Recurring musical theme" , "Recurrent theme" .)