In one's element when there's a party (2-4)
I believe the answer is:
at-home
This clue is a double definition.
'in one's element' is the first definition.
(I've seen this in another clue)
'there's a party' is the second definition.
(at home is a kind of party)
'when' is the link.
(Other definitions for at-home that I've seen before include "Domestic gathering" , "Reception at residence" , "Comfortable - in one's own country" , "In to callers" , "Reception in one's own abode" .)