Rabbit gently, at intervals, parting pair of bovines (6-3)
I believe the answer is:
yakety-yak
'rabbit' is the definition.
(I know that rabbit can be written as yakety-yak)
'gently at intervals parting pair of bovines' is the wordplay.
'at intervals' indicates alternate letters (letters are taken at regular intervals).
'parting' indicates putting letters inside.
'pair of' indicates the doubling of some letters (I've seen 'pair' mean this).
'bovines' becomes 'yak' (I can't explain this - if you can you should give a lot more credence to this answer).
The alternate letters of 'gently' are 'ety'.
'yak' duplicated is 'yakyak'.
'ety' placed into 'yakyak' is 'YAKETY-YAK'.
(Another definition for yakety-yak that I've seen is " stupid talk".)