By getting supper without drink (3)
I believe the answer is:
per
'by' is the definition.
(thesaurus)
'supper without drink' is the wordplay.
'without' suggests deleting specific letters.
'drink' becomes 'sup' (I've seen this before).
'supper' with 'sup' removed is 'PER'.
'getting' acts as a link.
(Other definitions for per that I've seen before include "Preposition meaning for each" , "For each or every" , "Preposition indicating by means of" , "According to" .)