Pictures group mountain climbing (6)
I believe the answer is:
plates
'pictures' is the definition.
(plate can mean an illustration in a book)
'group mountain climbing' is the wordplay.
'group' becomes 'set' (both can mean a collection).
'mountain' becomes 'alp' (the Alps are a mountain range).
'climbing' says the letters should be written backwards (in a down clue, letters climb up).
'set'+'alp'='setalp'
'setalp' reversed gives 'PLATES'.
(Other definitions for plates that I've seen before include "They're on the table" , "dentures" , "Shallow dishes" , "Strange staple for crockery items" , "Staple for food containers" .)