The most common and most likely answer to this crossword clue is the 9 letter word CELLULOID
I've seen this crossword clue in Independent
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More clues leading to the result CELLULOID
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The straight part
We know that "film" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case film = celluloid.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
Crossword Answer definitions
CELLULOID noun- Any of a variety of thermoplastics created from nitrocellulose and camphor, once used as photographic film.
- (often used attributively) The genre of cinema; film.