Savings plan letters (3)
I believe the answer is:
ira
'savings plan letters' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ira that I've seen before include "Illegal organisation, in short" , "George 13 down's brother" , "Illegal organisation, initially" , "Gershwin, say" , "Brother of George Gershwin" .)