Soft drink, please -- just half (6)
I believe the answer is:
supple
'soft' is the definition.
(thesaurus)
'drink please just half' is the wordplay.
'drink' becomes 'sup' (to sup is to drink).
'just half' means to take half the letters.
'please' cut in half is 'ple'.
'sup'+'ple'='SUPPLE'
(Other definitions for supple that I've seen before include "Opposite of stiff" , "Flexible, bending easily" , "Flexible, not stiff" , "Moving and bending with ease" , "Lissom" .)