Terribly vile leer — wake-up call (8)
I believe the answer is:
reveille
'wake-up call' is the definition.
(I've seen this before)
'terribly vile leer' is the wordplay.
'terribly' indicates anagramming the letters.
'vile'+'leer'='vileleer'
'vileleer' anagrammed gives 'REVEILLE'.
(Other definitions for reveille that I've seen before include "What soldiers get up to" , "Army waking signal" , "Early morning sound in the barracks" , "Early call" , "The get-out-of-bed bugle call" .)