About right, brief idea for currency (5)
I believe the answer is:
franc
'currency' is the definition.
(old French currency)
'about right brief idea' is the wordplay.
'about' indicates putting letters inside.
'right' becomes 'r' (common abbreviation).
'brief' means to remove the last letter (a shorter or briefer version of the word).
'idea' becomes 'fancy' (fancy is a kind of idea).
'fancy' with its final letter taken away is 'fanc'.
'r' placed inside 'fanc' is 'FRANC'.
'for' is the link.
(Other definitions for franc that I've seen before include "Swiss coin" , "Swiss monetary unit" , "Nonsense (colloq.)" , "Old French money" , "Former French monetary unit" .)