Monarch with bomb in fur (6)
I believe the answer is:
ermine
'fur' is the definition.
(ermine is a kind of fur)
'monarch with bomb' is the wordplay.
'monarch' becomes 'er' (abbreviation for Elizabeth Regina).
'with' says to put letters next to each other.
'bomb' becomes 'mine' (I've seen this before).
'er'+'mine'='ERMINE'
'in' acts as a link.
(Other definitions for ermine that I've seen before include "Stoat in its winter coat" , "special trimmings" , "Ceremonial fur" , "In mere strange fur" , "Animal with brown fur that turns white in winter" .)