Scottish promontory with a German plant (7)
I believe the answer is:
mullein
'plant' is the definition.
(mullein is a kind of plant)
'scottish promontory with a german' is the wordplay.
'scottish promontory' becomes 'mull'.
'with' says to put letters next to each other.
'a german' becomes 'ein' ('a' in German).
'mull'+'ein'='MULLEIN'
(Other definitions for mullein that I've seen before include "Yellow-flowered plant popularly known as Aaron's rod" , "Plant with spikes of yellow flowers" , "Plant with woolly leaves" .)