Stress rate applied to English unchanged (8)
I believe the answer is:
emphasis
'stress' is the definition.
(I know that stress can be written as emphasis)
'rate applied to english unchanged' is the wordplay.
'rate' becomes 'mph' (miles per hour).
'applied to' is a charade indicator (letters next to each other).
'english' becomes 'e' (abbreviation).
'unchanged' becomes 'as is' (as things currently are).
'mph' put after 'e' is 'emph'.
'emph'+'asis'='EMPHASIS'
(Other definitions for emphasis that I've seen before include "Stress given to a word" , "Special importance or significance" , "Stress, special importance" , "Intensity of expression" , "Stress - misshape (anag)" .)