Creature in a stream grabbing frantic duck (9)
I believe the answer is:
armadillo
'creature' is the definition.
(armadillo is a kind of creature)
'a stream grabbing frantic duck' is the wordplay.
'stream' becomes 'rill' (rill is a kind of stream**).
'grabbing' is an insertion indicator.
'frantic' becomes 'mad' ('mad' can be a synonym of 'frantic').
'duck' becomes 'o'.
'rill' placed around 'mad' is 'rmadill'.
'a'+'rmadill'+'o'='ARMADILLO'
'in' is the link.
(Other definitions for armadillo that I've seen before include "Scaly burrowing animal" , "bony individual?" , "Toothless Native American" , "Mammal with protective plates" , "Long-snouted animal" .)