Rich one leaping (9)
I believe the answer is:
abounding
'rich' is the definition.
(I've seen this before)
'one leaping' is the wordplay.
'one' becomes 'a'.
'leaping' becomes 'bounding' (bounding is a kind of leaping).
'a'+'bounding'='ABOUNDING'
(Other definitions for abounding that I've seen before include "in profusion" , "filled up" , "in huge numbers?" , "Plentiful" , "Rich" .)