Runs into an elderly poet (6)
I believe the answer is:
arnold
'poet' is the definition.
(19th-century poet Matthew Arnold)
'runs into an elderly' is the wordplay.
'runs' becomes 'r' (cricket abbreviation).
'into' means one lot of letters goes inside another.
'elderly' becomes 'old' (similar in meaning).
'r' going inside 'an' is 'arn'.
'arn'+'old'='ARNOLD'
(Other definitions for arnold that I've seen before include "Matthew --, English poet" , "-- Wesker, playwright" , "Overcome (obstacle)" , "Matthew --; -- Bennett" , "Victorian poet" .)