Beer initially on verge of running out? Calamity (4)
I believe the answer is:
blow
'calamity' is the definition.
(thesaurus)
'beer initially on verge of running out?' is the wordplay.
'initially' suggests taking the first letters.
'on' is a charade indicator (letters next to each other).
'verge of running out?' becomes 'low' (I can't explain this - if you can you should believe this answer much more).
The initial letter of 'beer' is 'b'.
'b'+'low'='BLOW'
Can you help me to learn more?
(Other definitions for blow that I've seen before include "Clip" , "Hit - disappointment" , "Strong current of air" , "cocaine from US" , "Whistle - hit" .)