Morgue's echo incredibly repugnant (8)
I believe the answer is:
gruesome
'repugnant' is the definition.
(I've seen this before)
'morgue's echo incredibly' is the wordplay.
'echo' becomes 'e' (phonetic alphabet: alpha, bravo, charlie etc.).
'incredibly' indicates anagramming the letters.
'morgues'+'e'='morguese'
'morguese' is an anagram of 'GRUESOME'.
(Other definitions for gruesome that I've seen before include "Causing horror or repulsion" , "terrible" , "Horrifying and revolting" , "Sickening, macabre" , "Repulsive, horrid" .)