In a frenzy, a mess (5)
I believe the answer is:
amuck
'in a frenzy' is the definition.
(I've seen this before)
'a mess' is the wordplay.
'mess' becomes 'muck' (I can't justify this - if you can you should give a lot more credence to this answer).
'a'+'muck'='AMUCK'
Can you help me to learn more?
(Other definitions for amuck that I've seen before include "Behaving disruptively" , "In a frenzy" , "Run this way to rush about violently and out of control" , "A mess gets one" .)