Roger Dean playing harmonium perhaps (4,5)
I believe the answer is:
reed organ
'harmonium perhaps' is the definition.
(I know that harmonium is a type of reed organ)
'roger dean playing' is the wordplay.
'playing' indicates an anagram.
'roger'+'dean'='rogerdean'
'rogerdean' with letters rearranged gives 'REED-ORGAN'.
(Other definitions for reed organ that I've seen before include "Keyboard instrument, harmonium" , "What you might hear" , "small instrument" , "supports traditional services" , "musical instrument" .)