Messy affairs bothered like-minded people (5,2,1,7)
I believe the answer is:
birds of a feather
'like-minded people' is the definition.
(I've seen this before)
'messy affairs bothered' is the wordplay.
'messy' indicates anagramming the letters.
'affairs'+'bothered'='affairsbothered'
'affairsbothered' is an anagram of 'BIRDS OF A FEATHER'.
(Other definitions for birds of a feather that I've seen before include "people of similar character" , "A kind" , "they combine well!" , "like-minded people" , "Like people" .)