Please reason step by step, and put your final answer within \boxed{}.
Given that \\(θ\\) is an angle in the fourth quadrant, and \\(\\sin (θ+ \\dfrac {π}{4})=- \\dfrac {3}{5}\\), find \\(\\tan (θ- \\dfrac {π}{4})=\\) \_\_\_\_\_\_.
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