A cereal with growing potential (5)
I believe the answer is:
acorn
'growing potential' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'a cereal' is the wordplay.
'cereal' becomes 'corn' (corn is a kind of cereal).
'a'+'corn'='ACORN'
'with' acts as a link.
Can you help me to learn more?
(Other definitions for acorn that I've seen before include "From which a "tall oak" may grow" , "Model in stone" , "Nut of oak tree" , "Dirt on a liquid surface" , "cup's content" .)