Race Comment Explainer

Original comment with matches highlighted:

in rear, headway from 2f out, for th final furlong, just held on for third post

Matched phrases & meanings

Phrase	Meaning
just held	The horse's powerful late run was not quite enough, and it lost the race by the narrowest possible margin (e.g., a nose or short head).
Furlong	Unit of distance; one furlong is 1/8 of a mile (approx. 200 meters).
Headway	The horse was moving up through the field.
Ran on	The horse maintained or increased its speed in the final stages.
Rear	Running near the back of the field.

Summary

The horse's powerful late run was not quite enough, and it lost the race by the narrowest possible margin (e.g., a nose or short head).
Unit of distance; one furlong is 1/8 of a mile (approx. 200 meters).
The horse was moving up through the field.
The horse maintained or increased its speed in the final stages.
Running near the back of the field.