"Speed" or perhaps "haste".
The word pace can be interpreted in many different ways. An eight letter word meaning pace is swiftness. This is a rapid pace.
What is the first letter of a five letter word meaning "pace"?
S is for speed.
S is for speed.
Tempo, or speed.
t for tempo
paces
t for tempo
tempo
t for tempo
If by pace you mean 's' for steps, 't' for tread, 'm' for march,
Speeds for speed, t for tempo