Abhorrent to Holmes, criminally hiding answer (9)
I believe the answer is:
loathsome
'abhorrent' is the definition.
(I've seen this before)
'to holmes criminally hiding answer' is the wordplay.
'criminally' indicates an anagram (I've seen this in other clues).
'hiding' means one lot of letters goes inside another.
'answer' becomes 'a' (abbreviation eg in Q and A).
'to'+'holmes'='toholmes'
'toholmes' is an anagram of 'lothsome'.
'lothsome' going around 'a' is 'LOATHSOME'.
(Other definitions for loathsome that I've seen before include "Disgusting, nauseating" , "Horrid" , "gross" , "Repulsive" , "Hateful" .)