Nominal figure about right (5)
I believe the answer is:
token
'nominal' is the definition.
(I know that nominal can be written as token)
'figure about right' is the wordplay.
'figure' becomes 'ten' (ten is a number).
'about' indicates putting letters inside.
'right' becomes 'ok' (OK can mean right or appropriate).
'ten' going around 'ok' is 'TOKEN'.
(Other definitions for token that I've seen before include "without meaning it" , "Done only as a symbolic gesture" , "Keepsake or memorial as of friendship" , "Done for appearance's sake" , "Counter" .)