Every so often repair organ (3)
I believe the answer is:
ear
'organ' is the definition.
(the ear is an organ)
'every so often repair' is the wordplay.
'every so often' means one should take alternating letters.
The alternating letters of 'repair' are 'EAR'.
(Other definitions for ear that I've seen before include "Place for a plug" , "Discernment musicians need" , "It's used in hearing" , "Heed" , "one hears" .)