Figure serving up seasonal drink soon (7)
I believe the answer is:
nonagon
'figure' is the definition.
(type of geometrical figure)
'up seasonal drink soon' is the wordplay.
'up' says the letters should be written backwards (in down clue: letters go upwards).
'seasonal drink' becomes 'nog' (I've seen this in another clue).
'soon' becomes 'anon' (synonyms).
'nog'+'anon'='noganon'
'noganon' written backwards gives 'NONAGON'.
'serving' acts as a link.
(Other definitions for nonagon that I've seen before include "Nine sided figure" , "Figure with nine sides" , "Figure with nine, twenty-one Dn" , "geometric figure" , "regular figure" .)