I'm nude, with a gin, dancing: that's unforeseen (10)
I believe the answer is:
unimagined
'unforeseen' is the definition.
(not previously imagined or thought of)
'i'm nude with a gin dancing' is the wordplay.
'with' means one lot of letters go next to another.
'dancing' is an anagram indicator.
'im'+'nude'+'a'+'gin'='imnudeagin'
'imnudeagin' is an anagram of 'UNIMAGINED'.
'that's' acts as a link.
(Other definitions for unimagined that I've seen before include "Not thought of" , "Not foreseen" .)