Unfortunately I step on it, a plant with brightly coloured leaves (10)
I believe the answer is:
poinsettia
'plant with brightly coloured leaves' is the definition.
'poinsettia' can be an answer for 'plant' (I've seen this before). I am not sure about the 'with brightly coloured leaves' bit.
'unfortunately i step on it a' is the wordplay.
'unfortunately' indicates an anagram (a bad or unfortunate spelling).
'i'+'step'+'on'+'it'='isteponit'
'isteponit' anagrammed gives 'poinsetti'.
'poinsetti'+'a'='POINSETTIA'
Can you help me to learn more?
(Other definitions for poinsettia that I've seen before include "poisonous bush" , "Plant with showy bracts, usu. red, pink or white" , "bloom" , "Flower popular at Christmas" , "Ornamental house plant" .)