Condescend to frame small sketch (6)
I believe the answer is:
design
'sketch' is the definition.
(design is a kind of sketch)
'condescend to frame small' is the wordplay.
'condescend' becomes 'deign' (synonyms).
'to frame' is an insertion indicator.
'small' becomes 's' (abbreviation - e.g. clothes size).
'deign' placed around 's' is 'DESIGN'.
(Other definitions for design that I've seen before include "Prepare a plan for something to be made" , "Blueprint, sketch" , "project" , "End" , "Signed up for fashion plan" .)