See one enjoy a double (4-5)
I believe the answer is:
look-alike
'a double' is the definition.
(I know that double can be written as look-alike)
'see one enjoy' is the wordplay.
'see' becomes 'look' (I've seen this in another clue).
'one' becomes 'a' (a thing is one thing).
'enjoy' becomes 'like' (like can mean to appreciate or enjoy something).
'look'+'a'+'like'='LOOK-ALIKE'
(Other definitions for look-alike that I've seen before include "One who closely resembles another" , "Person/thing closely resembling another" , "One's double" , "Living image, double" , "Person closely resembling another, double" .)