Drink alone, having dismissed one and all (5)
I believe the answer is:
total
'all' is the definition.
(thesaurus)
'drink alone having dismissed one' is the wordplay.
'drink' becomes 'tot' (a small alcoholic drink).
'having dismissed' indicates named letters should be taken away.
'alone' with 'one' taken away is 'al'.
'tot'+'al'='TOTAL'
'and' acts as a link.
(Other definitions for total that I've seen before include "Complete, absolute" , "It might be grand" , "The whole, sum" , "Entirety" , "Full, entire amount" .)