Devon flower in spring (4)
I believe the answer is:
dart
I believe this clue is a double definition.
'devon flower' is the first definition.
(river in Devon - something which flows)
'spring' is the second definition.
(thesaurus)
'in' is the link.
(Other definitions for dart that I've seen before include "Move quickly and suddenly" , "shift fast" , "Small narrow pointed missile" , "Sudden quick movement" , "Move along rapidly and lightly" .)