A sin to grasp at riches, primarily (7)
I believe the answer is:
avarice
'a sin to grasp at riches primarily' is the definition.
I can't tell whether this defines the answer.
'a sin to grasp at riches primarily' is the wordplay.
'sin' becomes 'vice' ().
'to grasp' indicates putting letters inside.
'primarily' says to take the initial letters.
The first letters of 'at riches' is 'ar'.
'vice' enclosing 'ar' is 'varice'.
'a'+'varice'='AVARICE'
(Other definitions for avarice that I've seen before include "Parsimony" , "A deadly sin" , "One of seven deadly sins" , "Greed for gain" , "Greed, covetousness" .)