Piccadilly hotel (4)
I believe the answer is:
ritz
'piccadilly hotel' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for ritz that I've seen before include "Luxurious hotel" , "Swiss hotelier, who founded an international chain, d. 1918" , "(Expensive) London hotel" , "Ostentatious luxury" , "Piccadilly hotel" .)