Difficulty getting feathers dry (3,4)
I believe the answer is:
rub down
'dry' is the definition.
(I've seen this before)
'difficulty getting feathers' is the wordplay.
'difficulty' becomes 'rub' (rub can mean a difficulty or problem).
'getting' is a charade indicator (letters next to each other).
'feathers' becomes 'down' (down can mean bird feathers).
'rub'+'down'='RUB-DOWN'
(Other definitions for rub down that I've seen before include "Prepare eight ac with sandpaper, say" , "Drying - cleaning - grooming" , "Vigorous towelling" , "dry" , "Get ready to paint" .)