Continue to request one American flowering plant (7)
I believe the answer is:
begonia
'flowering plant' is the definition.
(begonia is a kind of flowering plant)
'continue to request one american' is the wordplay.
'continue' becomes 'on' (I've seen this in other clues).
'to' is a charade indicator (letters next to each other) (I've seen this in other clues).
'request' becomes 'beg' (begging is a kind of requesting).
'one' becomes 'i' (Roman numeral).
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'on' after 'beg' is 'begon'.
'begon'+'i'+'a'='BEGONIA'
(Other definitions for begonia that I've seen before include "Tropical plant" , "colourful flower" , "Common garden plant" , "bloomer" , "Herbaceous plant whose flowers have no petals" .)