Sign in laconic rework that one is incredibly unstable and likely to explode (8)
I believe the answer is:
volcanic
'sign in laconic rework that one is incredibly unstable and likely to explode' is the definition.
Both the answer and definition are adjectives. Maybe you can see an association between them that I don't see?
'sign in laconic rework' is the wordplay.
'sign in' becomes 'v' (I can't justify this - if you can you should give a lot more credence to this answer).
'rework' indicates anagramming the letters (I've seen 'reworked' mean this).
'laconic' is an anagram of 'olcanic'.
'v'+'olcanic'='VOLCANIC'
Can you help me to learn more?
(Other definitions for volcanic that I've seen before include "Liable to violent outbursts" , "Like pumice" , "Of Etna or Vesuvius?" , "Like lava, perhaps" , "Relating to mountains such as Vesuvius" .)