Linear regression - reduce degrees of freedom

I have a Pandas dataframe with columns like

Order     Balance     Profit cum (%)

I'm doing a linear regression

model_profit_tr = pd.ols(y=df_closed['Profit cum (%)'], x=df_closed['Order'])

The problem with this is that standard model is like (equation of a line that does not pass through the origin)

y = a * x + b

There is 2 degrees of freedom (a and b)

slope (a):

a=model_profit_tr.beta['x']

and intercept (b):

b=model_profit_tr.beta['intercept']

I'd like to reduce degree of freedom for my model (from 2 to 1) and I 'd like to have a model like

y = a * x