Soon chapter abandons one of its members (4)
I believe the answer is:
anon
'soon' is the definition.
(I've seen this before)
'chapter abandons one of its members' is the wordplay.
I cannot really see how this works, but
'one' could be 'an' (I've seen this in other clues) and 'an' is present in the answer.
'of' could be 'o' and 'o' is found within the answer.
A single letter 'n' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
(Other definitions for anon that I've seen before include "Presently - unattributed" , "devoid of credit" , "In a little while (informal)" , "In the near future" , "Shortly; unknown" .)