Untidy serving-men eat here (2,1,4)
I believe the answer is:
in a mess
'here' is the definition.
Both the definition and answer are singular nouns.
Perhaps you can see an association between them that I don't see?
'untidy serving-men eat' is the wordplay.
'untidy serving men' becomes 'ina' (I can't justify this - if you can you should give a lot more credence to this answer).
'eat' becomes 'mess' (messing is a kind of eating).
'ina'+'mess'='IN A MESS'
Can you help me to learn more?
(Other definitions for in a mess that I've seen before include "at sixes and sevens" , "Tucker here for Tommy" .)