German article on the Spanish source of wood (5)
I believe the answer is:
elder
'source of wood' is the definition.
(elder is a kind of tree)
'german article on the spanish' is the wordplay.
'german article' becomes 'der' (definite article in German).
'on' is a charade indicator (letters next to each other).
'the spanish' becomes 'el' ('the' in Spanish).
'der' put after 'el' is 'ELDER'.
(Other definitions for elder that I've seen before include "Older person - one's senior" , "Tribal advisor" , "Senior churchman - shrub" , "sort of statesman" , "Church official; tree" .)