White weasel tormented leaderless firemen (6)
I believe the answer is:
ermine
'white weasel' is the definition.
(I've seen this in another clue)
'tormented leaderless firemen' is the wordplay.
'tormented' indicates an anagram.
'leaderless' means to remove the first letter.
'firemen' with its first letter removed is 'iremen'.
'iremen' is an anagram of 'ERMINE'.
(Other definitions for ermine that I've seen before include "Winter fur of the stoat" , "Ceremonial fur" , "Fur trimming on royal robes" , "Fur-bearing mammal" , "Fur for an English judge" .)