Elegant American in final (4)
I believe the answer is:
neat
'elegant' is the definition.
(similar in meaning)
'american in final' is the wordplay.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'in' indicates putting letters inside.
'final' becomes 'net' (synonyms).
'a' going within 'net' is 'NEAT'.
(Other definitions for neat that I've seen before include "Elegant - cow (archaic)" , "cow maybe" , "Shipshape" , "Tidy and uncluttered" , "Straight - cool!" .)