I am on time for photograph (5)
I believe the answer is:
image
'photograph' is the definition.
(thesaurus)
'i am on time for' is the wordplay.
'i am' becomes 'im'.
'on' is a charade indicator (letters next to each other).
'time for' becomes 'age' (I've seen this in other clues).
'im'+'age'='IMAGE'
(Other definitions for image that I've seen before include "Likeness; statue" , "Picture (involving one letter change from 10)" , "Likeness or mental picture" , "Dead ringer" , "Effigy, icon" .)