Hack or bug? (3)
I believe the answer is:
nag
I believe this clue is a double definition.
'hack' is the first definition.
(I know that hack can be written as nag)
'bug?' is the second definition.
(I've seen this in another clue)
'or' acts as a link.
(Other definitions for nag that I've seen before include "Hack" , "Equine" , "Bother persistently" , "Scold; inferior horse" , "Annoy constantly" .)