Hi, I'm a new user of Mathematica. I have a question. When using the Plot within Manipulate, for instance with

Manipulate[Plot[Sin[a x], {x, 0, 2 Pi}], {a, 1, 10}]

all works fine if I move the slider. However, if I show the animation controls by clicking on the + on the right of the slider and enter manually the value of parameter 'a' instead of setting it with the slider, another twin plot appears below the current plot. I understand that this happens because the plot where I enter the value of 'a' becomes an Input of which the duplicate plot is the output, however I'd like to deal with just one plot. Is there a way to avoid the second plot appear when manually entering the parameter value?

Thank you in advance for your help.