Fanaticism making last character break real toy (8)
I believe the answer is:
zealotry
'fanaticism' is the definition.
(synonyms)
'last character break real toy' is the wordplay.
'last character' becomes 'Z'.
'break' is an anagram indicator.
'real'+'toy'='realtoy'
'realtoy' anagrammed gives 'ealotry'.
'z'+'ealotry'='ZEALOTRY'
'making' acts as a link.
(Other definitions for zealotry that I've seen before include "Fanatical enthusiasm" , "Extremism" , "Excessive religious enthusiasm" , "Keenness" , "Fanatical behaviour" .)