Any actress should love him (5)
I believe the answer is:
oscar
'any actress' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'should love him' is the wordplay.
'should love' becomes 'os' (I am not sure about this - if you are sure you should believe this answer much more).
'him' becomes 'Car'.
'os'+'car'='OSCAR'
Can you help me to learn more?
(Other definitions for oscar that I've seen before include "-- Wilde, author" , "to wit involved in row" , "Librettist Hammerstein, d. 1960" , "Comms code for "O"" , "US film award" .)