Crucible's fading snooker shot (7,3)
I believe the answer is:
melting pot
'crucible's' is the definition.
(synonyms)
'fading snooker shot' is the wordplay.
'fading' becomes 'melting' (fading or melting away).
'snooker shot' becomes 'pot' (as in potting a ball in snooker).
'melting'+'pot'='MELTING-POT'
(Other definitions for melting pot that I've seen before include "Crucible'" , "Place where different peoples mingle" , "multicultural area" , "Vessel - place for mixture" , "In which to mix metals, immigrants" .)