A refuge for thieves maybe (3)
I believe the answer is:
den
'a refuge' is the definition.
(thesaurus)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for den that I've seen before include "Animals' shelter" , "Private office" , "Hidden lair of an animal" , "Animal's home or gent's study" , "Hiding place" .)