Sadly, hotelier’s lost cat (13)
I believe the answer is:
tortoiseshell
'cat' is the definition.
(tortoiseshell is a kind of cat)
'sadly hotelier's lost' is the wordplay.
'sadly' indicates an anagram.
'hoteliers'+'lost'='hotelierslost'
'hotelierslost' anagrammed gives 'TORTOISESHELL'.
(Other definitions for tortoiseshell that I've seen before include "Domestic cat - or little shoes (anag)" , "Mottled plated ornamental substance" , "Ornamental material" , "Butterfly - yellow-brown mottled material" , "Domestic cat mottled in brownish-yellow and black" .)