Can it take ages to grow? (4)
I believe the answer is:
'can' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'it take ages to grow?' is the wordplay.
'ages' can be anagrammed to 'SAGE'.
Though, I'm not sure how the anagram is indicated.
Can you help me to learn more?
(Other definitions for sage that I've seen before include "Aromatic herb" , "Savant" , "Clever" , "Feature of herb garden" , "cheesemongers associate with Derby" .)