What does the cryptic crossword clue "Boring, rubbish kind of humour (7)" mean?

The wordplay uses a charade (building blocks). DEAD (synonym="boring") + PAN (synonym="to rubbish, criticise") = DEADPAN The answer is DEADPAN.

Boring, rubbish kind of humour (7)

Guardian Cryptic #29254 | 23 Across | 2023-12-15 flower