Cold drink's rubbish – initially dismayed expression (6)
I believe the answer is:
crumbs
'cold drink's rubbish initially dismayed expression' is the definition.
I can't judge whether this definition defines the answer.
'cold drink's rubbish initially' is the wordplay.
'cold' becomes 'C' (eg on taps).
'drink' becomes 'rum' (rum is a kind of drink).
'rubbish initially' becomes 'bs' (I can't explain this - if you can you should believe this answer much more).
'c'+'rum'+'bs'='CRUMBS'
Can you help me to learn more?
(Other definitions for crumbs that I've seen before include "Exclamation of surprise" , "not much of a bloomer!" , "Surprised expression; bread fragments" , "that surprises me!" , "Little things offering minimal comfort" .)