Race Comment Explainer

Original comment with matches highlighted:

took keen hold, held up in imp, pushed along before 3 out, no impression,

Matched phrases & meanings

Phrase	Meaning
Pushed along	The jockey started to urge the horse (hand-riding, not necessarily using the whip).
tailed off	A definitive statement that the horse was finished and effectively out of the race
Held up	Intentionally raced patiently at the back to save energy.
Rear	Running near the back of the field.
Keen	The horse was fighting the jockey, wasting energy early.

Summary

The jockey started to urge the horse (hand-riding, not necessarily using the whip).
A definitive statement that the horse was finished and effectively out of the race
Intentionally raced patiently at the back to save energy.
Running near the back of the field.
The horse was fighting the jockey, wasting energy early.