Feature about American's restraint (5)
I believe the answer is:
chain
'restraint' is the definition.
(I know that chain is a type of restraint)
'feature about american's' is the wordplay.
'feature' becomes 'chin' (facial feature).
'about' indicates putting letters inside.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'chin' going around 'a' is 'CHAIN'.
(Other definitions for chain that I've seen before include "Rope of metal links" , "Length of pitch" , "Paper decoration" , "Wickets so far apart in cricket" , "Range of mountains" .)