Account repeated by one next to a shrub (6)
I believe the answer is:
acacia
'shrub' is the definition.
(I've seen this before)
'account repeated by one next to a' is the wordplay.
'account' becomes 'ac' (abbreviation).
'repeated' shows that letters should be duplicated.
'by' means one lot of letters go next to another.
'one' becomes 'i' (Roman numeral).
'next to' means one lot of letters go next to another.
'ac' doubled is 'acac'.
'acac'+'i'+'a'='ACACIA'
(Other definitions for acacia that I've seen before include "Flowering tree/shrub of Australia and Africa" , "Tree (wattle or robinia)" , "Type of shrub or tree" , "Spiny tree or shrub" , "Plant like wattle" .)