The question is asking you to evaluate the effects of a rise in income tax in the UK as a way to reduce the budget deficit.
This can include the effects on the budget deficit, AD and SRAS / LRAS.
Evaluate simply means to judge a statement by giving both sides of an argument.
For instance, you can argue that a rise in income tax can reduce the budget deficit - this is a good thing as it can reduce the crowding out effect. However, a rise in income tax can lead to a reduction in consumption leading to a fall in demand for goods and services - as the demand for labour is derived from the demand from goods and services, employment will fall, etc.
Tip - Use the mark scheme. This is not cheating. Use the mark scheme to help you build points to evaluate on. At the same time, check the examiners report - the examiner reports on how the student have answered the question and sometimes provide a common error students would often do when answering question.