Organ visibly smaller than the heart (3)
I believe the answer is:
ear
'organ' is the definition.
(the ear is an organ)
'visibly smaller than the heart' is the wordplay.
'EAR' is hidden in amongst the letters.
However, I am unsure how the hidden word is indicated.
Can you help me to learn more?
(Other definitions for ear that I've seen before include "Listening organ" , "Fruiting head of a cereal" , "Shell-like; corn" , "Bit of corn" , "Seed-bearing part of wheat" .)