In Act One I found a monkshood plant (7)
I believe the answer is:
aconite
'plant' is the definition.
(I know that aconite is a type of poisonous plant)
'in act one i found a monkshood' is the wordplay.
'act one i' anagrams to 'ACONITE'.
Though, I am unsure how this is indicated.
Can you help me to learn more?
(Other definitions for aconite that I've seen before include "Yellow-flowered plant" , "potential killer" , "Flower, for example monkshood or wolfsbane" , "Spring flower - poison" , "Poisonous flowering plant" .)