Were meandering around the south by river (5)
I believe the answer is:
weser
'river' is the definition.
(German river)
'were meandering around the south' is the wordplay.
'meandering' indicates an anagram.
'around' indicates putting letters inside.
'the south' becomes 's' (abbreviation).
'were' is an anagram of 'weer'.
'weer' enclosing 's' is 'WESER'.
'by' acts as a link.
(Other definitions for weser that I've seen before include "Er, sew up the German river" , "German runner" .)