Off-peak call (5)
I believe the answer is:
yodel
'call' is the definition.
(I know that yodel is a type of call)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for yodel that I've seen before include "Sing warblingly" , "Sing in traditional Swiss manner" , "Sing like the Lonely Goatherd?" , "Sing (Swiss style)" , "Alpine warble" .)