He can always ring up for cars (5)
I believe the answer is:
oscar
'he can always' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.
'ring up for cars' is the wordplay.
'ring' becomes 'o'.
'up for cars' becomes 'scar' (I am not sure about this - if you are sure you should believe this answer much more).
'o'+'scar'='OSCAR'
Can you help me to learn more?
(Other definitions for oscar that I've seen before include "Film statuette" , "to wit involved in row" , "One of several given to Chicago" , "One close to Mike" , "Boy" .)