Heron flying about European river (5)
I believe the answer is:
rhone
'european river' is the definition.
(I've seen this in another clue)
'heron flying' is the wordplay.
'flying' indicates an anagram (letters fly around into new positions).
'heron' with letters rearranged gives 'RHONE'.
'about' is the link.
(Other definitions for rhone that I've seen before include "wherein runs rain in Arbroath" , "wine-producing area" , "European river and glacier" , "River at Avignon and Arles" , "French wine region" .)