Determined to support policy that involves jumping forwards (4-3)
I believe the answer is:
line-out
'that involves jumping forwards' is the definition.
'determined to support policy' is the wordplay.
'determined' becomes 'out'.
'to support' means one lot of letters go next to another.
'policy' becomes 'line' (I've seen this before).
'out' after 'line' is 'LINE-OUT'.
(Other definitions for line-out that I've seen before include "Set piece of play in rugby" , "Outline for a rugby formation" , "RU throw-in" , "A standing rugby formation" , "Rugby re-start" .)