Humble compiler's ace in hole (6)
I believe the answer is:
demean
'humble' is the definition.
(demeaning is a kind of humbling)
'compiler's ace in hole' is the wordplay.
'compiler' becomes 'me' (the person who is writing these clues).
'ace' becomes 'a'.
'in' is an insertion indicator.
'hole' becomes 'den' (I've seen this in other clues**).
'me'+'a'='mea'
'mea' going into 'den' is 'DEMEAN'.
(Other definitions for demean that I've seen before include "'Put down, degrade (6)'" , "Stoop" , "Lower, degrade" , "disgrace" , "Degrade, abase" .)