Furious pace with pilot flying with the speed of light (10)
I believe the answer is:
apoplectic
'furious' is the definition.
'pace with pilot flying with the speed of light' is the wordplay.
'with' says to put letters next to each other.
'flying with' indicates an anagram (letters fly around into new positions).
'the speed of light' becomes 'c' (as in E=mc2).
'pace'+'pilot'='pacepilot'
'pacepilot' anagrammed with 'c' can make 'APOPLECTIC'.
(Other definitions for apoplectic that I've seen before include "Seeing red" , "Overcome with anger" , "With red vision" , "Outraged" .)