Awful toothache swallowing most of cold drink (3,9)
I believe the answer is:
hot chocolate
'drink' is the definition.
(hot chocolate is a kind of drink)
'awful toothache swallowing most of cold' is the wordplay.
'awful' indicates anagramming the letters.
'swallowing' indicates putting letters inside.
'most of' means to remove the last letter.
'toothache' is an anagram of 'hotchoate'.
'cold' with its last letter taken away is 'col'.
'hotchoate' going around 'col' is 'HOT CHOCOLATE'.
(Other definitions for hot chocolate that I've seen before include "Bedtime drink" , "Drink with cocoa powder" , "Beverage" , "Warming drink" , "Warm drink" .)