How to get this low contrast washed flared look for portraits in lightroom
You could use the Clarity slider but go negative on it and that will soften the look. However that will apply it to the whole image, whereas this looks like it was done selectively (one way in camera would be to apply vaseline to a clear filter).
To replicate that, use the Adjustment Brush to paint various areas you want to soften and then apply the Negative Clarity. Play with a few of the other Adjustment Brush sliders to change exposure and saturation to refine.