@thewordpage
The Times blog has appeared today for this crossword (later than usual) and the expert states
" 22. Instinctive representation of feet as hot? (4-2-3-5)
SEAT-OF-THE-PANTS: One of those reverse thingies where the answer thinks it’s the clue. Looking that way round, “PANTS” is the anagram indicator, (SEAT OF THE*) is the fodder, giving a representation of “FEET AS HOT”.
Hope you are happier about the clue and the parsing now :)