Poems on genuine hollowed out rocks (6)
I believe the answer is:
geodes
'rocks' is the definition.
'poems on genuine hollowed out' is the wordplay.
'poems' becomes 'odes' (ode is a kind of poem).
'on' says to put letters next to each other.
'hollowed out' says to hollow out the word (remove centre letters).
'genuine' with its centre removed is 'ge'.
'odes' after 'ge' is 'GEODES'.
(Other definitions for geodes that I've seen before include "Rock cavities lined with crystals - see dog (anag)" , "Stones" .)