Boring, rubbish kind of humour (7)
I believe the answer is:
deadpan
'kind of humour' is the definition.
Both the definition and answer are adjectives. Maybe you can see a link between them that I don't see?
'boring rubbish' is the wordplay.
'boring' becomes 'dead' (I've seen this in other clues).
'rubbish' becomes 'pan' (both can mean to criticise heavily).
'dead'+'pan'='DEADPAN'
Can you help me to learn more?
(Other definitions for deadpan that I've seen before include "Betraying no emotion" , "Serious-looking" , "Poker-faced" , "Blank" , "Keeping a straight face" .)