Collection of pictures almost entirely of poor quality (5)
I believe the answer is:
album
'collection of pictures' is the definition.
'album' can be an answer for 'pictures' (I've seen this before). I'm not certain of the 'collection of' bit.
'almost entirely of poor quality' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'entirely' becomes 'all' (I've seen this before).
'of poor quality' becomes 'bum' (I am not sure about this - if you are sure you should believe this answer much more).
'all' with its final letter removed is 'al'.
'al'+'bum'='ALBUM'
Can you help me to learn more?
(Other definitions for album that I've seen before include "CD, say" , "Book for displaying a collection" , "Recording; book" , "Blank book for mounting photos, stamps etc" , "Item of music released" .)