Reddish brown, some of these pianos (5)
I believe the answer is:
sepia
'reddish brown' is the definition.
(synonyms)
'of these pianos' is the wordplay.
'of' says the answer is hidden in the clue.
'SEPIA' is hidden within 'these pianos'.
'some' is the link.
(Other definitions for sepia that I've seen before include "Brown colour of old photo" , "Brown tint" , "Pigment obtained from cuttlefish ink" , "Brown tone associated with old photographs" , "brownish colour" .)