A tree line meets a couple of plants (5)
I believe the answer is:
rowan
'a tree' is the definition.
(type of tree)
'line meets a couple of plants' is the wordplay.
'line' becomes 'row' (a row or line of things).
'meets' is a charade indicator (letters next to each other).
'a couple of plants' becomes 'an' (I can't explain this - if you can you should give a lot more credence to this answer).
'row'+'an'='ROWAN'
Can you help me to learn more?
(Other definitions for rowan that I've seen before include "The mountain ash tree" , "ash native to mountain regions" , "Mr Atkinson, actor" , "-- Williams, theologian" , "Atkinson or Williams" .)