Fruit for a painful condition (5)
I believe the answer is:
acorn
'painful condition' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'fruit for a' is the wordplay.
'fruit' becomes 'corn' (corn is a kind of fruit).
'for' means one lot of letters go next to another (I've seen this in other clues).
'corn' put after 'a' is 'ACORN'.
Can you help me to learn more?
(Other definitions for acorn that I've seen before include "Model in stone" , "Oak seed" , "From which a "tall oak" may grow" , "Source of a great oak" , "Tree seed" .)