A small figure is not what's wanted for growth (4)
I believe the answer is:
weed
'wanted for growth' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'a small figure is not' is the wordplay.
I cannot really understand how this works, but
'small' could be 'wee' (Scottish term for small) and 'wee' is found within the answer.
A single letter 'd' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
'what's' is the link.
Can you help me to learn more?
(Other definitions for weed that I've seen before include "Work in garden" , "dope" , "gone!" , "Troublesome plant" , "Got rid of water" .)