Writing certain to lose initial consistency (7)
I believe the answer is:
texture
'consistency' is the definition.
(consistency can mean something's texture or feel)
'writing certain to lose initial' is the wordplay.
'writing' becomes 'text' (text is a kind of writing).
'certain' becomes 'sure' (synonyms).
'to lose initial' means to remove the first letter (I've seen 'losing initial' mean this).
'sure' with its initial letter taken away is 'ure'.
'text'+'ure'='TEXTURE'
(Other definitions for texture that I've seen before include "Appearance or feel of a surface" , "Consistency" , "Quality or feel of material" , "Quality of fabric" , "Feel of a woven fabric" .)