A number of picturesque pieces (6)
I believe the answer is:
mosaic
'pieces' is the definition.
(I have seen 'Little pieces' mean 'mosaic' so perhaps 'pieces' could also mean 'mosaic')
'a number of picturesque' is the wordplay.
'a number' becomes 'M' (M is an example).
'of' becomes 'o''.
'picturesque' becomes 'saic' (I can't explain this - if you can you should believe this answer much more).
'm'+'o'+'saic'='MOSAIC'
Can you help me to learn more?
(Other definitions for mosaic that I've seen before include "Decorative work of small hard pieces" , "Small square in pattern" , "Artistic design of glass or stones" , "Inlaid stone decoration" , "Design of small pieces of colored stone or glass (6)." .)