One might be coming or going (6)
I believe the answer is:
gerund
'be coming or going' is the definition.
(I've seen this in another clue)
'one' is the wordplay.
I cannot really understand how this works, but
'one' could be 'un' (northern English dialect form of 'one') and 'un' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
'might' is the link.
Can you help me to learn more?
(Other definitions for gerund that I've seen before include "Verb form functioning as a noun" , "Noun formed from a verb - red gun (anag)" , "Verb form used as a noun" , "item of grammar" , "Noun formed from a verb -- nudger (anag)" .)