Ultimately Michelle Obama abandoned a simple life (6)
I believe the answer is:
amoeba
'a simple life' is the definition.
(I've seen this in another clue)
'ultimately michelle obama abandoned' is the wordplay.
'ultimately' says to take the final letters.
'abandoned' is an anagram indicator (the original order is abandoned).
The last letter of 'michelle' is 'e'.
'e'+'obama'='eobama'
'eobama' with letters rearranged gives 'AMOEBA'.
(Other definitions for amoeba that I've seen before include "shape-shifter" , "Not much life" , "One-celled animal found in water" , "Basic life form" , "Constantly-changing one-celled creatures" .)