Wreck business with introduction of hopeless rep (7)
I believe the answer is:
torpedo
'wreck' is the definition.
(I've seen this before)
'business with introduction of hopeless rep' is the wordplay.
'business' becomes 'todo' (I can't explain this - if you can you should believe this answer much more).
'with introduction of' means one lot of letters goes inside another.
'hopeless' indicates an anagram.
'rep' anagrammed gives 'rpe'.
'todo' enclosing 'rpe' is 'TORPEDO'.
Can you help me to learn more?
(Other definitions for torpedo that I've seen before include "To wreck" , "Trooped (anag.)" , "Self-propelled marine weapon" , "Explosive underwater weapon" , "Sea-borne missile" .)