Old man running up and down (3)
I believe the answer is:
dad
This clue is a double definition.
'old man' is the first definition.
(both can mean one's father)
'running up and down' is the second definition.
(Other definitions for dad that I've seen before include "Relation" , "Father, in short" , "Pop, pater" , "Mum's mate" , "Old man" .)