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' indicates the doubling of some letters.
'by' means one lot of letters go next to another.
'one' becomes 'i' (Roman numeral).
'with' means one lot of letters go next to another.
'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" .)