White stone in altar base cracked (9)
I believe the answer is:
alabaster
'white stone' is the definition.
(I've seen this before)
'altar base cracked' is the wordplay.
'cracked' is an anagram indicator.
'altar'+'base'='altarbase'
'altarbase' is an anagram of 'ALABASTER'.
'in' is the link.
(Other definitions for alabaster that I've seen before include "Translucent white gypsum as found carved into ornaments" , "White mineral used for carving" , "Sculptors work with this" , "Altar base (anagr.)" , "Carved form of gypsum" .)