Bits of old verse periodically appearing as part of today's theme (4)
I believe the answer is:
'bits of old verse' is the definition.
'odes' can be an answer for 'verse' (I've seen this before). I'm not sure about the 'bits of old' bit.
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for odes that I've seen before include "To a Skylark, To a Nightingale etc", "verse", "Works by Pindar", "Poems in praise", "Lines".)