Collection of photographs of a large bottom (5)
I believe the answer is:
album
'collection of photographs' is the definition.
(I've seen this before)
'a large bottom' is the wordplay.
'large' becomes 'L' (eg in clothes sizes).
'bottom' becomes 'bum' (synonyms).
'a'+'l'+'bum'='ALBUM'
'of' is the link.
(Other definitions for album that I've seen before include "Record with multiple tracks" , "Photograph/stamp book" , "Blank book for keeping stamps, photographs etc" , "Item of music released" , "Recording; book" .)