Easy profit making my poor donor feel upset (5,3,3,4)
I believe the answer is:
money for old rope
'easy profit' is the definition.
(I've seen this before)
'my poor donor feel upset' is the wordplay.
'upset' is an anagram indicator.
'my'+'poor'+'donor'+'feel'='mypoordonorfeel'
'mypoordonorfeel' with letters rearranged gives 'MONEY FOR OLD ROPE'.
'making' acts as a link.
(Other definitions for money for old rope that I've seen before include "A piece of cake" , "dealing with elderly guys?" , "Profit for little effort" , "Reward for little effort" , "Easy profit" .)