Weed provided by fellow impresario (4)
I believe the answer is:
wimp
'weed' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'provided by fellow impresario' is the wordplay.
'provided by' says the answer is hidden in the clue (the answer is provided within the clue).
'WIMP' is hidden in the letters of 'fellow impresario'.
Can you help me to learn more?
(Other definitions for wimp that I've seen before include "Wet" , "one of the Tory wets?" , "Softy" , "Feeble or ineffective person" , "Puny, pathetic individual" .)