Feature of really rich poem (5)
I believe the answer is:
lyric
'poem' is the definition.
(I know that lyric is a type of poem)
'feature of really rich' is the wordplay.
'feature of' indicates a hidden word.
'LYRIC' is hidden within 'really rich'.
(Other definitions for lyric that I've seen before include "Of poetry that expresses the poet's feelings" , "Of poetry that expresses thoughts and feelings" , "in musical" , "something to sing about? On the contrary" , "Text of a popular song" .)