Middleman insolvent by end of year (6)
I believe the answer is:
broker
'middleman' is the definition.
(thesaurus)
'insolvent by end of year' is the wordplay.
'insolvent' becomes 'broke' (I've seen this in another clue).
'by' says to put letters next to each other.
'end of' indicates one should take the final letters.
The last letter of 'year' is 'r'.
'broke'+'r'='BROKER'
(Other definitions for broker that I've seen before include "Negotiate with" , "Insurance or investment agent" , "Financial dealer" , "One acts as an agent for others in buying and selling" , "See 16" .)