Seize revolutionary eastern boat (5)
I believe the answer is:
barge
'boat' is the definition.
(I know that barge is a type of boat)
'seize revolutionary eastern' is the wordplay.
'seize' becomes 'grab' (grabbing is a kind of seizing).
'revolutionary' shows that the letters should be reversed in order (letters revolve around).
'eastern' becomes 'e'.
'grab' written backwards gives 'barg'.
'barg'+'e'='BARGE'
(Other definitions for barge that I've seen before include "Bump" , "Move roughly; boat" , "Long boat for freight" , "Jostle; a boat" , "River transport" .)