Unacceptable band sketch (7)
I believe the answer is:
outline
'sketch' is the definition.
(I know that sketch can be written as outline)
'unacceptable band' is the wordplay.
'unacceptable' becomes 'out' (I've seen this before).
'band' becomes 'line' (band can mean a strip or line).
'out'+'line'='OUTLINE'
(Other definitions for outline that I've seen before include "Trace - form" , "Plan with little detail" , "(Make a) sketch" , "Preliminary draft" , "General plan; summary" .)