Concurred not to start vice (5)
I believe the answer is:
greed
'vice' is the definition.
(I've seen this before)
'concurred not to start' is the wordplay.
'concurred' becomes 'agreed' ('agree' can be a synonym of 'concur').
'not to start' means to remove the first letter.
'agreed' with its first letter taken away is 'GREED'.
(Other definitions for greed that I've seen before include "Craving" , "Eager desire" , "Insatiability" , "Covetousness" , "Wanting too much" .)