Missing first dance, policeman comes in for a drink (7)
I believe the answer is:
alcopop
'drink' is the definition.
(type of alcoholic drink)
'missing first dance policeman comes in for a' is the wordplay.
'missing first dance' becomes 'lop' (I am not sure about this - if you are sure you should believe this answer much more).
'policeman' becomes 'cop' (slang term).
'comes in' indicates putting letters inside.
'for' is a charade indicator (letters next to each other) (I've seen this in other clues).
'lop' placed around 'cop' is 'lcopop'.
'lcopop' after 'a' is 'ALCOPOP'.
Can you help me to learn more?
(Other definitions for alcopop that I've seen before include "Intoxicating beverage looking like a soft drink" , "Liquor drink for kids" , "It tastes like a soft drink, but isn't!" , "Hard drink resembling a soft drink" , "Intoxicating beverage tasting like a soft drink" .)