Threatening to have no more room for packages? (7)
I believe the answer is:
baleful
'threatening' is the definition.
(I know that threatening can be written as baleful)
I can't explain the rest of the clue.
(Other definitions for baleful that I've seen before include "Menacing - vindictive" , "Menacing - dejected" , "Menacing - gloomy" , "Malignant" , "threatening appearance?" .)