Still on a rocking horse? (8)
I believe the answer is:
stallion
'horse?' is the definition.
(thesaurus)
'still on a rocking' is the wordplay.
'rocking' indicates an anagram.
'still'+'on'+'a'='stillona'
'stillona' anagrammed gives 'STALLION'.
(Other definitions for stallion that I've seen before include "Mount" , "Uncastrated adult male horse" , "Male steed" , "Male horse kept for breeding" , "Mare's mate" .)