What is the ruling on a clear fluid coming out after urination? Is it Wadi? How does one perform Ghusl from it? Is Wudu required to wash it off? And what should I do if it comes out before prayer and I fear it will come out during it?

It appears that the discharge is wadi, and its ruling is the same as that of urine. It is impure and invalidates ablution (wudu'). Therefore, it must be cleansed, and ablution must be performed for anything requiring ritual purity. If its emission is continuous, your ruling is that of someone afflicted with incontinence (sals); you perform wudu' for each prayer after its time has begun, take precautions, and pray both the obligatory and supererogatory prayers with that wudu'. Neither a ritual bath (ghusl) nor wudu' is required of you unless you intend to perform an act that necessitates wudu'. If it exits immediately after urination, wait a little and then purify yourself after it. Do not search for it, and do not let doubts cause you to miss congregational prayer. Address these doubts by ignoring them. If you prayed and then found something had exited, your prayer is valid; because if the time of an impurity's occurrence is doubted, it is attributed to the nearest possible time of its exit. The default is the validity of the prayer, and that nothing invalidates it unless by certainty.