The most common and most likely answer to this crossword clue is the 7 letter word TRAILER
I've seen this crossword clue in The Times
T
R
A
I
L
E
R
More clues leading to the result TRAILER
- Something for transporting creeping plant
- Vehicle in on-screen advertisement
- Creeping plant in American’s caravan
- Advance publicity identifying towed vehicle
- Advertisement that’s likely to be pulled?
- Preview of what follows 19
- Creeping plant in house on wheels
- Whinger after time finds what’s behind truck
- Line in sort of artier short film
- … vehicle clip from Terminator?
Buddy explains!

The straight part
We know that "Vehicle/on-screen advertisement" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case vehicle/on-screen advertisement = trailer.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 TRAILER mean?
TRAILER noun- Someone who or something that trails.
- Part of an object which extends some distance beyond the main body of the object.
- An unpowered wheeled vehicle, not a caravan or camper, that is towed behind another, and used to carry equipment, etc, that cannot be carried in the leading vehicle.
- A furnished vehicle towed behind another, and used as a dwelling when stationary; a caravan; a camper.
- A prefabricated home that could be towed to a new destination but is typically permanently left in an area designated for such homes.
- A preview of a film, video game or TV show.
- A short blank segment of film at the end of a reel, for convenient insertion of the film in a projector.
- The final record of a list of data items, often identified by a key field with an otherwise invalid value that sorts last alphabetically (e.g., “ZZZZZ”) or numerically (“99999”); especially common in the context of punched cards, where the final card is called a trailer card.
- The last part of a packet, often containing a check sequence.
- To load on a trailer or to transport by trailer.