Dog's cry (4)
(Other definitions for yelp that I've seen before include "Little dog's bark" , "Short sharp cry or bark" , "Sharp shrill cry of dog (4)" , "Painful sound" , "Short sharp cry (of such as a dog)" .)
'dog's cry' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for bark that I've seen before include "Section of tree" , "Outer covering of tree" , "Outside of a tree" , "Woof" , "possibly causing alarm in 23 [CATTERY] ?" .)