Warble trillingly in Arroyo del Sur (5)
I believe the answer is:
yodel
'warble' is the definition.
(I know that warble can be written as yodel)
'in arroyo del sur' is the wordplay.
'in' says the answer is hidden in the clue.
'YODEL' is hidden in the letters of 'arroyo del sur'.
'trillingly' acts as a link.
I am not very happy about this link. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for yodel that I've seen before include "Sing falsetto like Swiss mountain people" , "Sing using falsetto" , "Sing in intermittent falsetto" , "Vocalise" , "Alpine mountain call" .)