A cereal with fruit (5)
I believe the answer is:
acorn
'fruit' is the definition.
(I know that acorn is a type of fruit)
'a cereal' is the wordplay.
'cereal' becomes 'corn' (corn is a kind of cereal).
'a'+'corn'='ACORN'
'with' acts as a link.
(Other definitions for acorn that I've seen before include "Potential oak" , "Tree seed" , "From which a mighty oak may grow?" , "Model in stone" , "Potentially future tree" .)