Cake brought into a disco in great supply (9)
I believe the answer is:
abundance
'great supply' is the definition.
(I've seen this in another clue)
'cake brought into a disco' is the wordplay.
'cake' becomes 'bun' (bun is a type of cake).
'brought into' means one lot of letters goes inside another.
'disco' becomes 'dance' (I've seen this in other clues).
'a'+'dance'='adance'
'bun' put within 'adance' is 'ABUNDANCE'.
'in' acts as a link.
(Other definitions for abundance that I've seen before include "Plenty, profusion" , "'Plenty, loads (9)'" , "Ban due can be plenty" , "great amount" , "Plenitude" .)