Liberal friend across German river (8)
I believe the answer is:
moderate
'liberal' is the definition.
The answer and definition can be both people as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'friend across german river' is the wordplay.
'friend' becomes 'mate' (mate is a kind of friend).
'across' indicates putting letters inside.
'german river' becomes 'oder' (River Oder in central Europe).
'mate' going around 'oder' is 'MODERATE'.
Can you help me to learn more?
(Other definitions for moderate that I've seen before include "Dare me to (anag) - act as an arbitrator" , "Reduce" , "Not extreme - not very good" , "not going to extremes" , "Not excessively right- or left-wing" .)