Mike, northern runner, sees rodent (5)
I believe the answer is:
mouse
'rodent' is the definition.
(mouse is a kind of rodent)
'mike northern runner' is the wordplay.
'mike' becomes 'M' (phonetic alphabet: alpha, bravo, charlie etc.).
'northern runner' becomes 'ouse' (Yorkshire river. I am not sure about the 'northern' bit.).
'm'+'ouse'='MOUSE'
'sees' acts as a link.
Can you help me to learn more?
(Other definitions for mouse that I've seen before include "shy and timid type" , "underhand office worker?" , "Cursor control" , "Quiet person" , "See 1 down" .)