Seats of old empire gone with onset of socialism (8)
I believe the answer is:
ottomans
'seats' is the definition.
(Ottoman is a type of seat)
'old empire gone with onset of socialism' is the wordplay.
'old empire' becomes 'ottoman' (Ottoman Empire).
'gone with' means one lot of letters go next to another.
'onset of' suggests taking the first letters.
The initial letter of 'socialism' is 's'.
'ottoman'+'s'='OTTOMANS'
'of' is the link.
(Other definitions for ottomans that I've seen before include "Low seats or footstools" , "Residents of former Turkish Empire" , "Turkish seats" , "Old Turks or long cushioned seats" , "Old Turks, or cushioned seats without backs or sides" .)