Move mules -- both stripped part of plant (5)
I believe the answer is:
ovule
'part of plant' is the definition.
(part of a plant's ovary)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for ovule that I've seen before include "Part of plant ovary which becomes seed" , "Part of flower" , "Part of seed plants" , "Small body containing the female germ cell of a plant" , "Egg cell" .)