Account by a group of spies - one is a plant (6)
I believe the answer is:
acacia
'plant' is the definition.
(acacia is a kind of plant)
'account by a group of spies one' is the wordplay.
'account' becomes 'ac'.
'by' says to put letters next to each other.
'group of spies one' becomes 'cia' (I can't explain this - if you can you should give a lot more credence to this answer).
'ac'+'a'+'cia'='ACACIA'
'is a' is the link.
Can you help me to learn more?
(Other definitions for acacia that I've seen before include "Thorny tree, wattle" , "Tree or shrub with yellow or white flowers" , "Wattle genus" , "Gum-yielding tree ir shrub" , "Plant such as the Australian wattle" .)