River is treacly, dead in places (5)

I believe the answer is:
clyde
'river' is the definition.
(I've seen this before)
'treacly dead in places' is the wordplay.
'CLYDE' is hidden within the letters.
But, I am uncertain how the hidden word is indicated.
'is' acts as a link.
Can you help me to learn more?
(Other definitions for clyde that I've seen before include "bank robber" , "Glasgow's river" , "Glasgow river" , "River of western Scotland" , "Flower of Scotland" .)
