Old fellow one's run into at station (6)
I believe the answer is:
buffer
This clue is a double definition.
'old fellow' is the first definition.
(buffer can informally mean an elderly man)
'one's run into at station' is the second definition.
(type of piston on a railway track)
(Other definitions for buffer that I've seen before include "Shock absorber, it lessens impact" , "Thing or structure that lessens effect of impact" , "Protect against shock" , "Shock absorber - ineffectual fellow" , "It lessons the force of an impact, something in between" .)