Cuss the rotten mango with dead ends inside (7)
I believe the answer is:
goddamn
'cuss the' is the definition.
I can't tell whether this defines the answer.
'rotten mango with dead ends inside' is the wordplay.
'rotten' indicates anagramming the letters.
'with dead ends' becomes 'dd' (I can't explain this - if you can you should give a lot more credence to this answer).
'inside' indicates putting letters inside.
'mango' with letters rearranged gives 'goamn'.
'goamn' enclosing 'dd' is 'GODDAMN'.
Can you help me to learn more?
(Other definitions for goddamn that I've seen before include "expletive" , "Blasted - odd G-man (anag)" .)