Lily needs a drink (4)
I believe the answer is:
arum
'lily' is the definition.
(a type of lily)
'a drink' is the wordplay.
'drink' becomes 'rum' (rum is a kind of drink).
'a'+'rum'='ARUM'
'needs' is the link.
(Other definitions for arum that I've seen before include "Cuckoo-pint" , "plant with a white spathe" , "Perennial" , "Plant of the family Araceae, eg lords-and-ladies" , "Type of 1 Across" .)