Notice a poisonous plant (7)
I believe the answer is:
aconite
'plant' is the definition.
The answer is an example.
'notice a poisonous' is the wordplay.
'poisonous' indicates anagramming the letters (I've seen this in other clues).
'notice'+'a'='noticea'
'noticea' is an anagram of 'ACONITE'.
(Other definitions for aconite that I've seen before include "Poisonous flowering plant" , "Yellow-flowered plant" , "Spring flower - poison" , "Flower, for example monkshood or wolfsbane" , "potential killer" .)