Excellent returns by accounts in plant (6)
I believe the answer is:
acacia
'in plant' is the definition.
'acacia' can be an answer for 'plant' (I've seen this before). I'm not sure about the 'in' bit.
'excellent returns by accounts' is the wordplay.
'excellent' becomes 'ai' (resembles 'A1', old-fashioned term for excellent).
'returns' shows that the letters should be reversed in order.
'by' says to put letters next to each other.
'accounts' becomes 'acac' (two ac abbreviation).
'ai' back-to-front is 'ia'.
'ia' after 'acac' is 'ACACIA'.
Can you help me to learn more?
(Other definitions for acacia that I've seen before include "Thorny shrub with yellow or white-flowers" , "Spiny tree or shrub" , "Flowering tree/shrub of Australia and Africa" , "Flowering tree or shrub" , "Wattle that grows" .)