It may be held in revulsion (4)
I believe the answer is:
nose
'revulsion' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'it may be' is the wordplay.
I cannot quite understand how this works, but
'it' could be 'e' ('e' can mean 'electronic' which is similar to 'IT') and 'e' is present in the answer.
The remaining letters 'nos' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'held in' is the link.
Can you help me to learn more?
(Other definitions for nose that I've seen before include "Informer" , "Conk (slang)" , "Schnozzle" , "Facial feature" , "Deserving blame" .)