The most common and most likely answer to this crossword clue is the 6 letter word HAMMER
I've seen this crossword clue in Financial Times
H
A
M
M
E
R
More clues leading to the result HAMMER
- Slate someone acting ineptly?
- Pound of meat, paltry end cut
- Basic problem at home wounded me right through the heart
- Slam source of horror films?
- Horror film-maker‘s hit?
- Band returning after Meat Is Murder
- Shape of a twice-married female externally
- Bone meat and cut nothing more
- Footballer who gives unconvincing performance?
- Criticise novel rejected inside 60 minutes
Buddy explains!

The straight part
We know that "Slam/source of horror films" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case slam/source of horror films = hammer.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 HAMMER mean?
HAMMER noun- A tool with a heavy head and a handle used for pounding.
- The act of using a hammer to hit something}}
- A moving part of a firearm that strikes the firing pin to discharge a gun.
- The malleus, a small bone of the middle ear.
- In a piano or dulcimer, a piece of wood covered in felt that strikes the string.
- A device made of a heavy steel ball attached to a length of wire, and used for throwing.
- The last stone in an end.
- (frisbee) A frisbee throwing style in which the disc is held upside-down with a forehand grip and thrown above the head.
- Part of a clock that strikes upon a bell to indicate the hour.
- One who, or that which, smites or shatters.
- To strike repeatedly with a hammer, some other implement, the fist, etc.
- To form or forge with a hammer; to shape by beating.
- To emphasize a point repeatedly.
- To hit particularly hard.
- To ride very fast.
- To strike internally, as if hit by a hammer.
- To defeat (a person, a team) resoundingly
- To make high demands on (a system or service).
- To declare (a person) a defaulter on the stock exchange.
- To beat down the price of (a stock), or depress (a market).
- To have hard sex with