Race Comment Explainer

Original comment with matches highlighted:

held up in sion, ridden before last, no impression run-in

Matched phrases & meanings

Phrase	Meaning
ridden before	The jockey started urging the horse aggressively before the second-last obstacle to try and get it back into contention.
Held up	Intentionally raced patiently at the back to save energy.
Rear	Running near the back of the field.

Summary

The jockey started urging the horse aggressively before the second-last obstacle to try and get it back into contention.
Intentionally raced patiently at the back to save energy.
Running near the back of the field.