Robin runs into ruddy animal (9)
I believe the answer is:
redbreast
'robin' is the definition.
('redbreast' can be a synonym of 'robin')
'runs into ruddy animal' is the wordplay.
'runs' becomes 'r' (cricket abbreviation).
'into' means one lot of letters goes inside another.
'ruddy' becomes 'red' ('red' can be a synonym of 'ruddy').
'animal' becomes 'beast' ('beast' can be a synonym of 'animal'**).
'red'+'beast'='redbeast'
'r' going within 'redbeast' is 'REDBREAST'.
(Other definitions for redbreast that I've seen before include "Bird" , "Type of robin" , "One tweets" , "Flapper" .)