Furious about it after computer's last bug (8)
I believe the answer is:
irritate
'bug' is the definition.
(I've seen this before)
'furious about it after computer's last' is the wordplay.
'furious' becomes 'irate' (I've seen this before).
'about' is an insertion indicator.
'after' is a charade indicator (letters next to each other).
'last' indicates one should take the final letters.
The last letter of 'computer' is 'r'.
'it' after 'r' is 'rit'.
'irate' enclosing 'rit' is 'IRRITATE'.
(Other definitions for irritate that I've seen before include "Vex, aggravate" , "badger" , "'Annoy, vex (8)'" , "Provoke" , "Wind up" .)