One picking up scraps in general mess (7)
I believe the answer is:
gleaner
'one picking up scraps' is the definition.
(a gleaner gathers small pieces of something)
'general mess' is the wordplay.
'mess' indicates anagramming the letters.
'general' with letters rearranged gives 'GLEANER'.
'in' is the link.
(Other definitions for gleaner that I've seen before include "Description of Ruth" , "farm worker" , "Person gathering" , "Leftover grain gatherer" , "One gathering (grain) after a harvest" .)