Fellow, elderly, to cease trading (4)
I believe the answer is:
fold
'cease trading' is the definition.
(I've seen this before)
'fellow elderly' is the wordplay.
'fellow' becomes 'F' (abbreviation - of a society etc.).
'elderly' becomes 'old' (similar in meaning).
'f'+'old'='FOLD'
'to' is the link.
(Other definitions for fold that I've seen before include "Collapse; bend in half" , "Members of church" , "enclosure" , "Prepare pages to put in small envelope" , "Congregation; (firm) go bankrupt" .)