Undeveloped seed (5)
I believe the answer is:
ovule
'undeveloped seed' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ovule that I've seen before include "Part of seed plants" , "Part of flower" , "Immature ovum" , "Undeveloped seed" , "Small plant structure that develops into a seed" .)