Gnome mounted horse to cross gorge (7)
I believe the answer is:
epigram
'gnome' is the definition.
(thesaurus)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for epigram that I've seen before include "Gnome" , "it might be natural to wag" , "Short witty remark" , "Bon mot" , "Short, memorable saying" .)