...support on paper, so relax (5,4)
I believe the answer is:
stand down
'relax' is the definition.
Both the definition and answer are verbs in their base form.
Perhaps there's a link between them I don't understand?
'support on paper' is the wordplay.
'support' becomes 'stand' (stand is a kind of support).
'on paper' becomes 'down' (I can't justify this - if you can you should give a lot more credence to this answer).
'stand'+'down'='STAND DOWN'
'so' acts as a link.
Can you help me to learn more?
(Other definitions for stand down that I've seen before include "Relinquish one's post" , "Resign (from office)" , "Withdraw; go off duty" , "Withdraw as from competition, be seated" , "Quit" .)