Sure worried about old currency (5)
I believe the answer is:
euros
'currency' is the definition.
(I've seen this before)
'sure worried about old' is the wordplay.
'worried' indicates an anagram (worry can mean to interfere with or disturb).
'about' is an insertion indicator.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'sure' anagrammed gives 'eurs'.
'eurs' going around 'o' is 'EUROS'.
(Other definitions for euros that I've seen before include "Monetary units" , "French coins and notes" , "money" , "Rouse (anag.)" , "Continental currency units" .)