A drop of drink, right? (4)
I believe the answer is:
tear
'a drop' is the definition.
(thesaurus)
'drink right?' is the wordplay.
'drink' becomes 'tea' (tea is a kind of drink).
'right?' becomes 'r' (common abbreviation).
'tea'+'r'='TEAR'
'of' acts as a link.
(Other definitions for tear that I've seen before include "Optical sign of sorrow" , "Hurry" , "wrench" , "Shred" , "Small globule of sorrow" .)