Don went down with a cry of pain (6)
I believe the answer is:
fellow
'don' is the definition.
(thesaurus)
'went down with a cry of pain' is the wordplay.
'went down' becomes 'fell'.
'with' says to put letters next to each other.
'a cry of pain' becomes 'ow' (I've seen this in other clues).
'fell'+'ow'='FELLOW'
(Other definitions for fellow that I've seen before include "Bloke; senior member of college" , "Neglected child" , "Boy or man" , "Companion or associate" , "Colleague" .)