It has its vacationist side (3)
I believe the answer is:
sea
'vacationist side' is the definition.
The definition and answer can be both natural objects as well as being singular nouns.
Perhaps you can see a link between them that I don't see?
'it has its' is the wordplay.
'it' becomes 'sa' (old-fashioned abbreviation for sex appeal).
'has' means one lot of letters goes inside another.
'its' becomes 'e' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'sa' enclosing 'e' is 'SEA'.
Can you help me to learn more?
(Other definitions for sea that I've seen before include "Adriatic, for example" , "It's stocked with fish" , "Body of saltwater" , "Expanse of salt water" , "The Med, e.g." .)