The most common and most likely answer to this crossword clue is the 7 letter word TRELLIS
I've seen this crossword clue in The Times
T
R
E
L
L
I
S
More clues leading to the result TRELLIS
- In brief, run is for trainer
- Support I’ll back, beset by endless stress
- Return of stone edging even less healthy for plant support
- Rest breaks around bad climbing frame
- Likely backer where climbers need training
- Runs to stop rat on one’s garden frame
- Inform island about right climber's aid
- Archer hugging climber at last on island where climbers are trained
- State is defending Republican support for plants
- Archer is about right, training climbers on it
Buddy explains!

The straight part
We know that "trainer" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case trainer = trellis.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 TRELLIS mean?
TRELLIS noun- An outdoor garden frame that can be used for partitioning a common area.
- An outdoor garden frame that can be used to grow vines or other climbing plants.
- A kind of graph, used in communication theory and encryption, whose nodes are ordered into vertical slices by time, with each node at each time connected to at least one node at an earlier and at least one node at a later time.
- To train or arrange (plants) so that they grow against a trellis.