Sculpt exterior with writing (4)
I believe the answer is:
text
'writing' is the definition.
(text is a kind of writing)
'sculpt exterior with' is the wordplay.
'with' indicates a hidden word.
'TEXT' is hidden within 'sculpt exterior'.
(Other definitions for text that I've seen before include "Writing or printing" , "inspiration for sermon" , "Written material for study" , "piece of writing" , "Words of a book" .)