Brush off small tree (5)
I believe the answer is:
shrub
'small tree' is the definition.
The answer and definition can be both plants as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'brush off' is the wordplay.
'off' is an anagram indicator.
'brush' with letters rearranged gives 'SHRUB'.
Can you help me to learn more?
(Other definitions for shrub that I've seen before include "Small woody plant" , "Mixed drink of rum, sugar, fruit-juice and spice" , "Plant - brush (anag)" , "Perhaps Heather" , "Myrtle or Rosemary, say" .)