1
general::
Phrase(s): hot on something
Fig. enthusiastic about something; very much interested in something; knowledgeable about something. • Meg’s hot on animal rights. • Jean is hot on modern ballet just now.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
1. Also, hot for. Enthusiastic about, as in She's really hot on golf, or He's hot for another skiing vacation. This seemingly modern slangy usage was first recorded in 1667. Also see MAKE IT HOT FOR. 2. Also, hot at. Very good, impressive, as in He's hot at anything involving numbers. This expression, first recorded in 1573, is frequently used in the negative, as in I'm not so hot at new computer programs.
American Heritage Idioms