Label fresh meat for packing in horse box (4,3)
I believe the answer is:
name tag
'label' is the definition.
(name tag is a kind of label)
'fresh meat for packing in horse box' is the wordplay.
I cannot really see how this works, but
an anagram of 'meat' is 'amet' which is present in the answer.
'horse' could be 'nag' (term for an old horse) and 'nag' is found in the leftover letters.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for name tag that I've seen before include "verifies one's identity" , "Form of ID" , "A magnet (anag) - identification" , "sign of identification" , "Identifying badge" .)