Account repeated by one with a plant (6)
I believe the answer is:
acacia
'plant' is the definition.
The answer is an example.
'account repeated by one with a' is the wordplay.
'account' becomes 'ac' (abbreviation for account).
'repeated' says to double the letters.
'by' says to put letters next to each other.
'one' becomes 'i' (Roman numeral).
'with' says to put letters next to each other.
'ac' duplicated is 'acac'.
'acac'+'i'+'a'='ACACIA'
(Other definitions for acacia that I've seen before include "Subtropical shrub or tree" , "Wattle genus" , "Australian shrub" , "Spiny tree or shrub" , "Plant like wattle" .)