Slow-moving creatures torment mottled cat (13)
I believe the answer is:
tortoiseshell
'cat' is the definition.
(tortoiseshell is a kind of cat)
'slow-moving creatures torment mottled' is the wordplay.
I cannot quite see how this works, but
'torment' could be 'hell' and 'hell' is located in the answer.
The remaining letters 'tortoises' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for tortoiseshell that I've seen before include "Mottled plated ornamental substance" , "Butterfly - yellow-brown mottled material" , "Domestic cat - or little shoes (anag)" , "Domestic cat mottled in brownish-yellow and black" , "The case of the slow-moving" .)