Plenty of cake in a cakewalk, say (9)
I believe the answer is:
abundance
'plenty' is the definition.
(I've seen this before)
'cake in a cakewalk say' is the wordplay.
'cake' becomes 'bun' (I've seen this before).
'in' means one lot of letters goes inside another.
'cakewalk say' becomes 'dance' (cakewalk is a kind of dance).
'a'+'dance'='adance'
'bun' going into 'adance' is 'ABUNDANCE'.
'of' acts as a link.
(Other definitions for abundance that I've seen before include "Ample sufficiency or great plenty." , "call at whist" , "great deal" , "Danube can flow with plenty" , "Plethora" .)