A lot of sheepdogs flit about showing maximum pace? (5,2,5)

I believe the answer is:
speed of light
'maximum pace?' is the definition.
The answer and definition can be both related to time as well as being singular nouns.
Maybe there's a link between them I don't understand?
'a lot of sheepdogs flit about' is the wordplay.
'a lot of' means to remove the first letter.
'about' is an anagram indicator.
'sheepdogs'+'flit'='sheepdogsflit'
'sheepdogsflit' with its initial letter removed is 'heepdogsflit'.
'heepdogsflit' is an anagram of 'SPEED OF LIGHT'.
'showing' is the link.
Can you help me to learn more?
(Other definitions for speed of light that I've seen before include "The c in Einstein's equation" , "299,792,458 meters per second" , "The c in E=mc 2" , "299,792,458 metres per second" .)
