Old man grabbing eastern bird’s plume (7)
I believe the answer is:
feather
'bird's plume' is the definition.
'feather' can be an answer for 'plume' ('feather' can be a synonym of 'plume'). I'm not sure about the 'bird's' bit.
'old man grabbing eastern' is the wordplay.
'old man' becomes 'father' (I've seen this before).
'grabbing' indicates putting letters inside.
'eastern' becomes 'e'.
'father' placed around 'e' is 'FEATHER'.
(Other definitions for feather that I've seen before include "Part of a bird's plumage" , "trifling thing" , "Part of covering of bird" , "Free hat (anag)" , "In your cap, it's an accomplishment" .)