Something boring on deck, a sanction for servicemen (4,5)
I believe the answer is:
pack drill
'a sanction for servicemen' is the definition.
(military punishment)
'something boring on deck' is the wordplay.
'something boring' becomes 'drill' (drills bore into things).
'on' means one lot of letters go next to another.
'deck' becomes 'pack'.
'drill' put after 'pack' is 'PACK-DRILL'.
(Other definitions for pack drill that I've seen before include "Military punishment" , ""No names, no _____"" .)