First in carvery, order unseasoned beef (8)
I believe the answer is:
complain
'beef' is the definition.
(I've seen this in another clue)
'first in carvery order unseasoned' is the wordplay.
'first in carvery' becomes 'c' (pst letter of 'carvery').
'order' becomes 'om' (Order of Merit).
'unseasoned' becomes 'plain' (I can't explain this - if you can you should believe this answer much more).
'c'+'om'+'plain'='COMPLAIN'
Can you help me to learn more?
(Other definitions for complain that I've seen before include "Bellyache" , "Lament" , "Grizzle" , "Grumble, carp" , "Grumble, moan" .)