One tragically set up new hotel on foundationless lot (7)
I believe the answer is:
othello
'foundationless lot' is the definition.
I can't judge whether this defines the answer.
'one tragically set up new hotel on' is the wordplay.
'one tragically set' becomes 'ol' (I can't explain this - if you can you should give a lot more credence to this answer).
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'new' indicates anagramming the letters.
'on' is a charade indicator (letters next to each other).
'ol' in reverse letter order is 'lo'.
'hotel' anagrammed gives 'othel'.
'lo' put after 'othel' is 'OTHELLO'.
Can you help me to learn more?
(Other definitions for othello that I've seen before include "player from Stratford" , "Shakespeare hero" , "jealous husband" , "Shakespeare's tragic Moor of Venice" , "Eponymous hero" .)