Some humorous sarcasm held up as insensitive (5)
I believe the answer is:
crass
'insensitive' is the definition.
(a crass comment might be insensitive)
'some humorous sarcasm held up' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'held up' says the letters should be written in reverse.
'ssarc' is hidden within 'humorous sarcasm'.
'ssarc' back-to-front is 'CRASS'.
'as' acts as a link.
(Other definitions for crass that I've seen before include "Totally lacking in sensibility" , "Tactless, boorish" , "'Gross, vulgar (5)'" , "Grossly stupid, tactless" , "Unrefined" .)