Whole of a litre after dram (5)
I believe the answer is:
total
'whole' is the definition.
(total is a kind of whole)
'a litre after dram' is the wordplay.
'litre' becomes 'L' (abbreviation).
'after' is a charade indicator (letters next to each other).
'dram' becomes 'tot' (I've seen this in another clue).
'a'+'l'='al'
'al' put after 'tot' is 'TOTAL'.
'of' is the link.
(Other definitions for total that I've seen before include "Completely destroy" , "Ruin" , "Comprising the whole" , "Entirety" , "Comprehensive" .)