Dropped in for a cold drink (3)
I believe the answer is:
ice
'dropped in' is the definition.
The definition and answer can be both substances as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'for a cold drink' is the wordplay.
'for' becomes 'ie' (I can't justify this - if you can you should give a lot more credence to this answer).
'a cold' becomes 'c' (abbreviation, eg on taps).
'drink' indicates putting letters inside.
'ie' going around 'c' is 'ICE'.
Can you help me to learn more?
(Other definitions for ice that I've seen before include "Glaciate" , "Freeze" , "To put in a drink or slide on" , "Precious stones" , "Form of water" .)