Farm animal breaking speed of light ... take off ... lift off! (8)
I believe the answer is:
sheepdog
'farm animal' is the definition.
(type of farm animal)
'speed of light take off lift off' is the wordplay.
'take off' is a deletion indicator.
'off' indicates an anagram.
'speed'+'of'+'light'='speedoflight'
'speedoflight' with 'lift' removed is 'speedogh'.
'speedogh' anagrammed gives 'SHEEPDOG'.
'breaking' is the link.
I am not very happy about this link. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for sheepdog that I've seen before include "Working farm animal" , "Farmer's herding helper" , "One drives over fields" , "could it be Old English?" , "Pastoral assistant?" .)