Share American plant (5)
I believe the answer is:
lotus
'plant' is the definition.
(lotus is a flowering plant)
'share american' is the wordplay.
'share' becomes 'lot' (lot can mean a share or portion).
'american' becomes 'US' (United States).
'lot'+'us'='LOTUS'
(Other definitions for lotus that I've seen before include "Sacred waterlily" , "Car manufacturer - plant" , "British sports and racing car manufacturer" , "Mythical fruit including stste of dreaminess" , "Fruit of forgetfulness - water lily - car marque" .)