Alternately, dirty, intense, and ultimately hilarious feature of some humour (7)
I believe the answer is:
dryness
'feature of some humour' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'alternately dirty intense and ultimately hilarious' is the wordplay.
'alternately' means one should take alternating letters.
'and' means one lot of letters go next to another.
'ultimately' says to take the final letters.
The last letter of 'hilarious' is 's'.
'dirty'+'intense'='dirtyintense'
The alternate letters of 'dirtyintense' are 'drynes'.
'drynes'+'s'='DRYNESS'
Can you help me to learn more?
(Other definitions for dryness that I've seen before include "Aridity" , "Freedom from moisture" , "Lack of moisture" , "Matter-of-fact quality (of humour)" , "producing thirst" .)