Nature is adapting, beginning to make medicinal fluid (9)
I believe the answer is:
antiserum
'medicinal fluid' is the definition.
(I've seen this before)
'nature is adapting beginning to make' is the wordplay.
'adapting' indicates anagramming the letters.
'beginning to' says to take the initial letters.
The initial letter of 'make' is 'm'.
'nature'+'is'='natureis'
'natureis' is an anagram of 'antiseru'.
'antiseru'+'m'='ANTISERUM'
(Other definitions for antiserum that I've seen before include "bloody stuff" , "shot" , "treatment against disease" , "Injection; I'm at nurse (anag.)" , "Medicinal fluid" .)