Insect causing program problem (3)
I believe the answer is:
This clue is a double definition.
'insect' is the first definition.
(bug is a kind of insect)
'program problem' is the second definition.
(I've seen this in another clue)
'causing' is the link.
(Other definitions for bug that I've seen before include "Computer program error" , "Small crawling creature, now in computer programs" , "Tap" , "Annoy; insect" , "An enthusiast" .)