A bit upset, OK, about packing an old crate (6)
I believe the answer is:
dakota
'an old crate' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'a bit upset ok about packing' is the wordplay.
'bit' becomes 'tad' (both can mean a small amount).
'upset' is a reversal indicator.
'about' indicates anagramming the letters.
'packing' indicates putting letters inside.
'a'+'tad'='atad'
'atad' in reverse letter order is 'data'.
'ok' anagrammed gives 'ko'.
'data' placed around 'ko' is 'DAKOTA'.
Can you help me to learn more?
(Other definitions for dakota that I've seen before include "North American Indian; Douglas DC-Three" , "US state, North or South" , "State < facts about completely stunning" , "Former US territory, now divided into two states" , "US territory split North and South" .)