The most common and most likely answer to this crossword clue is the 8 letter word GASLIGHT
I've seen this crossword clue in The Times
G
A
S
L
I
G
H
T
More clues leading to the result GASLIGHT
- Illumination breaking down halts gig
- Shoot the breeze with blonde in attempt to manipulate
- Silver reflected faint source of illumination
- Flame from lamp, silver, turned up a little
- Film of Georgia, inconsequential
- Lead in Godzilla, a modest film
- Give up on insignificant Bergman film
- Psychologically manipulate, generally starting with a disrespectful insult
- Greenery, at first a modest innovation in late Georgian streets
- Talk on fair’s source of illumination
Buddy explains!

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 = gaslight.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.
What does GASLIGHT mean?
GASLIGHT noun- A lamp which operates by burning piped illuminating gas.
- The light produced by the burning gas in such a lamp.
- To manipulate (someone) psychologically such that they question their own memory, perception, and sanity, thereby evoking in them cognitive dissonance and low self-esteem.