Abhorrent to Holmes, criminally hiding ace (9)
I believe the answer is:
loathsome
'abhorrent' is the definition.
(I've seen this before)
'to holmes criminally hiding ace' is the wordplay.
'criminally' indicates an anagram (I've seen this in other clues).
'hiding' indicates putting letters inside.
'ace' becomes 'a' (abbreviation).
'to'+'holmes'='toholmes'
'toholmes' with letters rearranged gives 'lothsome'.
'lothsome' going around 'a' is 'LOATHSOME'.
(Other definitions for loathsome that I've seen before include "Repulsive" , "Hateful" , "Horrid" , "gross" , "Disgusting, nauseating" .)