Understate the importance of pretend feathers (4,4)
I believe the answer is:
play down
'understate the importance' is the definition.
(I've seen this before)
'pretend feathers' is the wordplay.
'pretend' becomes 'play' (synonyms).
'feathers' becomes 'down' (down can mean bird feathers).
'play'+'down'='PLAY DOWN'
'of' is the link.
(Other definitions for play down that I've seen before include "Seek to lessen the importance (of something)" , "Understate the importance" , "Minimise the importance of (something)" , "Gloss over" , "Give little importance to" .)