Prostrate yourself! Rest on feathers! (3,4)
I believe the answer is:
lie down
'prostrate' is the definition.
(I know this)
'rest on feathers' is the wordplay.
'rest' becomes 'lie' (lying is a kind of resting).
'on' says to put letters next to each other.
'feathers' becomes 'down' (down can mean bird feathers).
'lie'+'down'='LIE-DOWN'
'yourself' is the link.
This may not be correct. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for lie down that I've seen before include "Put your feet up" , "Rest in a horizontal position" , "Now idle (anag) -- short rest" , "Take rest; be submissive (under)" , "Take a rest (at length!)" .)