An underground place of humiliation (9)
I believe the answer is:
abasement
'humiliation' is the definition.
(synonyms)
'an underground place' is the wordplay.
'an' becomes 'a'.
'underground place' becomes 'basement'.
'a'+'basement'='ABASEMENT'
'of' is the link.
(Other definitions for abasement that I've seen before include "Mean beast (anag.)" , "shame" , "Humiliation" , "that one humbly displays" , "degrading" .)