Puffed-up, vacuous gloater who deals in contraband (8)
I believe the answer is:
smuggler
'deals in contraband' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'puffed-up vacuous gloater' is the wordplay.
'puffed-up' becomes 'smug' (I've seen this in another clue).
'vacuous' means to remove the middle letters.
'gloater' with its middle taken out is 'gler'.
'smug'+'gler'='SMUGGLER'
'who' acts as a link.
Can you help me to learn more?
(Other definitions for smuggler that I've seen before include "Transporter of illegal goods" , "Exciseman's foe" , "Importer of goods without paying duties" , "Criminal" , "Runner" .)