Deification is heaps too silly (10)
I believe the answer is:
apotheosis
'deification' is the definition.
(I know that deification can be written as apotheosis)
'is heaps too silly' is the wordplay.
'silly' is an anagram indicator.
'is'+'heaps'+'too'='isheapstoo'
'isheapstoo' is an anagram of 'APOTHEOSIS'.
(Other definitions for apotheosis that I've seen before include "Highest point of development" , "Elevation to divine status" , "Crowning point" , "Perfect example" , "Model" .)