Last of ten should come to nothing (6)
I believe the answer is:
nought
'nothing' is the definition.
(synonyms)
'last of ten should' is the wordplay.
'last of' indicates one should take the final letters.
'should' becomes 'ought' (synonyms).
The last letter of 'ten' is 'n'.
'n'+'ought'='NOUGHT'
'come to' is the link.
(Other definitions for nought that I've seen before include "Love" , "Zilch" , "Zero" , "Poetically nothing" , "The figure 0" .)