Homework includes beginning to trim brown plant (7)
I believe the answer is:
dittany
'plant' is the definition.
(dittany is a kind of plant)
'homework includes beginning to trim brown' is the wordplay.
'homework' becomes 'diy' (DIY is work done on your home).
'includes' is an insertion indicator.
'beginning to' says to take the initial letters.
'brown' becomes 'tan' (tan is a kind of brown).
The first letter of 'trim' is 't'.
't'+'tan'='ttan'
'diy' enclosing 'ttan' is 'DITTANY'.
(Other definitions for dittany that I've seen before include "Aromatic plant" , "Shrub" , "oil-producer" .)