Dumb-ass banged baseless bass drum (6)
I believe the answer is:
absurd
'banged baseless bass drum' is the definition.
The answer and definition are not the same part of speech. However, past participle verbs and adjectives can occasionally define each other.
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for absurd that I've seen before include "Quite ridiculous, silly" , "Quite ridiculous, laughable" , "Incredible" , "Ludicrous, silly" , "Foolish, quite ridiculous" .)