Space for some oar movement (3,4)
I believe the answer is:
sea room
'space' is the definition.
(sea room is a kind of space)
'some oar movement' is the wordplay.
'movement' indicates an anagram (letters move around).
'some'+'oar'='someoar'
'someoar' anagrammed gives 'SEA-ROOM'.
'for' is the link.
(Other definitions for sea room that I've seen before include "required for naval manoeuvres" , "Space to manoeuvre" .)