Assuming as a name when one's business is collapsing (5,5)
I believe the answer is:
going under
'assuming' is the definition.
The answer and definition can be both to do with motion as well as being present participle verbs.
Perhaps they are linked in a way I don't understand?
'a name when one's business is collapsing' is the wordplay.
I cannot really see how this works, but
'name' could be 'gun' and 'gun' is found in the answer.
'one' could be 'i' (Roman numeral) and 'i' is located in the answer.
'when' could be 'on' (I've seen this in other clues) and 'on' is present in the remaining letters.
This may be the basis of the clue (or it may be nonsense).
'as' acts as a link.
Can you help me to learn more?
(Another definition for going under that I've seen is " Sinking, failing".)