Little daughter is growing wild (4)
I believe the answer is:
weed
'growing wild' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'little daughter' is the wordplay.
'little' becomes 'wee' (similar in meaning).
'daughter' becomes 'd' (genealogical abbreviation).
'wee'+'d'='WEED'
'is' acts as a link.
Can you help me to learn more?
(Other definitions for weed that I've seen before include "Uncultivated plant" , "dope" , "Plant growing where it is not wanted" , "Got rid of water" , "Wild unwanted plant - tobacco?" .)