Damage borne by sickbay in old European republic (3,6)
I believe the answer is:
san marino
'european republic' is the definition.
(I've seen this before)
'damage borne by sickbay in old' is the wordplay.
'damage' becomes 'mar' (to mar is to spoil or damage).
'borne by' means one lot of letters goes inside another (to bear can mean to carry).
'sickbay' becomes 'san' (I've seen this before).
'old' becomes 'o' (abbreviation).
'san'+'in'='sanin'
'mar' inserted into 'sanin' is 'sanmarin'.
'sanmarin'+'o'='SAN MARINO'
(Other definitions for san marino that I've seen before include "Small European state" , "Small independent republic in NE Italy" , "nation" , "Small state within Italy" , "Tiny European republic" .)