Bird calls spoil the speech (6)
I believe the answer is:
cheeps
'bird calls' is the definition.
(a cheep is a sound made by a bird)
'spoil the speech' is the wordplay.
'spoil' indicates an anagram.
'speech' anagrammed gives 'CHEEPS'.
(Other definitions for cheeps that I've seen before include "The sound" , "Bird sounds" , "as exemplified in some tweets" , "Speech like bird cries" .)