The most common and most likely answer to this crossword clue is the 4 letter word GRIP
G
R
I
P
More clues leading to the result GRIP
Buddy explains!

The straight part
We know that "Ditch/one on film set" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case ditch/one on film set = grip.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 GRIP mean?
GRIP verb- To take hold of, particularly with the hand.
- To help or assist, particularly in an emotional sense.
- To do something with another that makes you happy/gives you relief.
- To trench; to drain.
- A hold or way of holding, particularly with the hand.
- A handle or other place to grip.
- A visual component on a window etc. enabling it to be resized and/or moved.
- (film production) A person responsible for handling equipment on the set.
- A channel cut through a grass verge (especially for the purpose of draining water away from the highway).
- A lot of something.
- A long time.
- A small travelling-bag or gripsack.
- An apparatus attached to a car for clutching a traction cable.
- Assistance; help or encouragement.
- A helpful, interesting, admirable, or inspiring person.
- As much as one can hold in a hand; a handful.
- A tenacious grasp; a holding fast.
- A device for grasping or holding fast to something.
- Influenza, the flu.
- A small ditch or trench; a channel to carry off water or other liquid; a drain.
- The griffin.