Is it necessary to perform ghusl (ritual bathing) after every instance of sexual arousal or stimulation that leads to the emission of clear fluid that dampens the underwear, or is ghusl specific to sexual intercourse that necessitates janabah (a state of ritual impurity requiring ghusl)?

Ghusl (definition) (ritual bath) is not obligatory merely due to desire or arousal. Rather, it has known causes, such as sexual intercourse, the emission of semen with desire while awake or in a dream, or the cessation of menstruation and post-natal bleeding. The clear fluid the questioner sees after arousal is madhy (pre-seminal fluid), which does not necessitate ghusl, and prayer is valid without it. However, madhy is impure and nullifies ablution (wudu'), and whatever it touches on the body and clothes must be washed.