Unusually old paintings from the east (5)
I believe the answer is:
extra
'unusually' is the definition.
(extra can mean to an unusual degree)
'old paintings from the east' is the wordplay.
'old' becomes 'ex'.
'paintings' becomes 'art' (painting is a type of artwork).
'from the east' says the letters should be written backwards.
'art' backwards is 'tra'.
'ex'+'tra'='EXTRA'
(Other definitions for extra that I've seen before include "Bonus; surplus" , "Left over" , "Bye or wide, for example" , "Surplus to requirements" , "An increased amount" .)