A hundred remaining in the chasm (5)
I believe the answer is:
cleft
'chasm' is the definition.
(thesaurus)
'a hundred remaining' is the wordplay.
'a hundred' becomes 'c' (roman numeral).
'remaining' becomes 'left' ('left' can be a synonym of 'remaining'**).
'c'+'left'='CLEFT'
'in the' is the link.
(Other definitions for cleft that I've seen before include "Crack" , "Space" , "Split, divided" , "Partially divided" , "Narrow gap" .)