Unusual cave rite showing imagination (8)
I believe the answer is:
creative
'showing imagination' is the definition.
(I've seen this before)
'unusual cave rite' is the wordplay.
'unusual' indicates an anagram.
'cave'+'rite'='caverite'
'caverite' is an anagram of 'CREATIVE'.
(Other definitions for creative that I've seen before include "Reactive in artistic manner" , "Innovative in reactive way" , "Full of ideas" , "Imaginative, inventive" , "Showing imagination" .)