An example of perceived threat is client believing that are at risk of harm if they adhere to medical advice (eg severe side effects from taking a drug or withdrawal symptoms when giving up a substance).
What matters is understanding that the client perceives harm is likely, even when the true risk is tiny, hence finding ways to remove the fear is important.
Therefore, changing the client’s perception of threats is a useful target for improving adherence e.g: helping them think realistically about risk, whilst not minimising how they feel.