European left beside the German tree (5)
I believe the answer is:
elder
'tree' is the definition.
(elder is a kind of tree)
'european left beside the german' is the wordplay.
'european' becomes 'E' (abbreviation e.g. EU).
'left' becomes 'l' (common abbreviation).
'beside' is a charade indicator (letters next to each other) (I've seen this in other clues).
'the german' becomes 'der' ('the' in German).
'e'+'l'+'der'='ELDER'
(Other definitions for elder that I've seen before include "Layman of the church" , "White-flowered tree" , "Tree for a church senior" , "Senior churchman - shrub" , "Tie up" .)