Plant needs crazy amount of liquid (6,4)
I believe the answer is:
cuckoo pint
'plant' is the definition.
(cuckoo-pint is a kind of plant)
'crazy amount of liquid' is the wordplay.
'crazy' becomes 'cuckoo' (I've seen this before).
'amount of liquid' becomes 'pint' (pint is a unit of liquid volume).
'cuckoo'+'pint'='CUCKOO-PINT'
'needs' is the link.
(Other definitions for cuckoo pint that I've seen before include "Growth of members of the Upper House" , "lords and ladies" , "Plant" , "Grower" .)