Emaciated, wild elk eats leaves, primarily (8)
I believe the answer is:
skeletal
'emaciated' is the definition.
(synonyms)
'wild elk eats leaves primarily' is the wordplay.
'wild' is an anagram indicator.
'primarily' indicates taking the first letters.
The initial letter of 'leaves' is 'l'.
'elk'+'eats'='elkeats'
'elkeats' with letters rearranged gives 'skeleta'.
'skeleta'+'l'='SKELETAL'
(Other definitions for skeletal that I've seen before include "Consisting of bones" , "reduced to a minimum" , "Bony, gaunt" , "Pulchritude" , "wasted" .)