Explanation:

- The phrase “a secret plan, made to do something (usually wrong)” typically denotes actions that are hidden and often illicit or unethical.

- Option 1: Strategy - This generally refers to a carefully devised plan to achieve a goal but doesn’t inherently imply secrecy or wrongdoing.

- Option 2: Planning - It indicates organizing steps or processes to achieve something but lacks the essence of secrecy or intent to do wrong.

- Option 3: Conditioning - Relates to training or accustoming someone/something to behave in a certain way. Doesn’t imply planning or wrongdoing.

- Option 4: Conspiracy - This is indeed the word that means a secret plan, especially one aimed at doing something illegal.