Troublemaker finally blowing entrance off Vlad's castle (7)

I believe the answer is:

gremlin

I'm a little stuck... Click here to teach me more about this clue!

'troublemaker' is the definition.
(I've seen this before)

I can't explain the rest of the clue.

(Other definitions for gremlin that I've seen before include "Unexplained technical problem or fault" , "Mischievous goblin" , "Mechanical fault" , "Bug (in engine)" , "Troublemaking goblin" .)

I've seen this clue in The Independent.

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