Pictures created by writer -- one's a peculiar grey (7)
I believe the answer is:
imagery
'pictures created by writer' is the definition.
(as in poetic imagery)
'one's a peculiar grey' is the wordplay.
'one's' becomes 'I'm' ('one is' is a formal way of saying 'I am').
'peculiar' indicates anagramming the letters (a peculiar or strange ordering of the letters).
'grey' anagrammed gives 'gery'.
'im'+'a'+'gery'='IMAGERY'
(Other definitions for imagery that I've seen before include "statues etc." , "Figures of speech" , "Language that produces pictures in readers' minds" , "Vivid written or oral descriptions" , "Descriptive language" .)